現状

.NET Core 2.2のAngularテンプレートで開発中のものです。

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp2.2</TargetFramework>
    <TypeScriptCompileBlocked>true</TypeScriptCompileBlocked>
    <TypeScriptToolsVersion>Latest</TypeScriptToolsVersion>
    <IsPackable>false</IsPackable>
    <SpaRoot>ClientApp\</SpaRoot>
    <DefaultItemExcludes>$(DefaultItemExcludes);$(SpaRoot)node_modules\**</DefaultItemExcludes>

    <!-- Set this to true if you enable server-side prerendering -->
    <BuildServerSideRenderer>false</BuildServerSideRenderer>
    <AssemblyName>AppName</AssemblyName>
    <RootNamespace>AppName</RootNamespace>
    <Version>2.0.1</Version>
    <Authors>Bernardo Lloret-Fuentes</Authors>
    <Company>Bernardo Lloret-Fuentes</Company>
    <Product>ASP.NET Core 2.2 with Angular 7 Template</Product>
    <PackageId>ASP.NET Core 2.2 with Angular 7 Template</PackageId>
    <Description>ASP.NET Core 2.2 with Angular 7 Template</Description>
    <PackageProjectUrl>https://github.com/blfuentes/NETCore2_2_Angular7_Template</PackageProjectUrl>
    <RepositoryUrl>https://github.com/blfuentes/NETCore2_2_Angular7_Template</RepositoryUrl>
    <StartupObject>AppName.Program</StartupObject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.AspNetCore.SpaServices.Extensions" Version="2.2.0" />
    <PackageReference Include="Microsoft.Extensions.Http" Version="2.2.0" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.2.3" />
  </ItemGroup>

  <ItemGroup>
    <!-- Don't publish the SPA source files, but do show them in the project files list -->
    <Content Remove="$(SpaRoot)**" />
    <None Include="$(SpaRoot)**" Exclude="$(SpaRoot)node_modules\**" />
  </ItemGroup>

  <Target Name="DebugEnsureNodeEnv" BeforeTargets="Build" Condition=" '$(Configuration)' == 'Debug' And !Exists('$(SpaRoot)node_modules') ">
    <!-- Ensure Node.js is installed -->
    <Exec Command="node --version" ContinueOnError="true">
      <Output TaskParameter="ExitCode" PropertyName="ErrorCode" />
    </Exec>
    <Error Condition="'$(ErrorCode)' != '0'" Text="Node.js is required to build and run this project. To continue, please install Node.js from https://nodejs.org/, and then restart your command prompt or IDE." />
    <Message Importance="high" Text="Restoring dependencies using 'npm'. This may take several minutes..." />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm install" />
  </Target>

  <Target Name="PublishRunWebpack" AfterTargets="ComputeFilesToPublish">
    <!-- As part of publishing, ensure the JS resources are freshly built in production mode -->
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm install" />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm run build -- --prod" />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm run build:ssr -- --prod" Condition=" '$(BuildServerSideRenderer)' == 'true' " />

    <!-- Include the newly-built files in the publish output -->
    <ItemGroup>
      <DistFiles Include="$(SpaRoot)dist\**; $(SpaRoot)dist-server\**" />
      <DistFiles Include="$(SpaRoot)node_modules\**" Condition="'$(BuildServerSideRenderer)' == 'true'" />
      <ResolvedFileToPublish Include="@(DistFiles->'%(FullPath)')" Exclude="@(ResolvedFileToPublish)">
        <RelativePath>%(DistFiles.Identity)</RelativePath>
        <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
      </ResolvedFileToPublish>
    </ItemGroup>
  </Target>

  <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
    <TypeScriptTarget>ES2015</TypeScriptTarget>
    <TypeScriptJSXEmit>None</TypeScriptJSXEmit>
    <TypeScriptModuleKind>ES6</TypeScriptModuleKind>
    <TypeScriptCompileOnSaveEnabled>True</TypeScriptCompileOnSaveEnabled>
    <TypeScriptNoImplicitAny>False</TypeScriptNoImplicitAny>
    <TypeScriptRemoveComments>False</TypeScriptRemoveComments>
    <TypeScriptOutFile />
    <TypeScriptOutDir />
    <TypeScriptGeneratesDeclarations>False</TypeScriptGeneratesDeclarations>
    <TypeScriptNoEmitOnError>True</TypeScriptNoEmitOnError>
    <TypeScriptSourceMap>True</TypeScriptSourceMap>
    <TypeScriptMapRoot />
    <TypeScriptSourceRoot />
  </PropertyGroup>

  <ProjectExtensions><VisualStudio><UserProperties appsettings_1json__JsonSchema="" /></VisualStudio></ProjectExtensions>

</Project>

更新後

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <TypeScriptCompileBlocked>true</TypeScriptCompileBlocked>
    <TypeScriptToolsVersion>Latest</TypeScriptToolsVersion>
    <IsPackable>false</IsPackable>
    <SpaRoot>ClientApp\</SpaRoot>
    <DefaultItemExcludes>$(DefaultItemExcludes);$(SpaRoot)node_modules\**</DefaultItemExcludes>

    <!-- Set this to true if you enable server-side prerendering -->
    <BuildServerSideRenderer>false</BuildServerSideRenderer>
    <AssemblyName>AppName</AssemblyName>
    <RootNamespace>AppName</RootNamespace>
    <Version>2.0.1</Version>
    <Authors>Bernardo Lloret-Fuentes</Authors>
    <Company>Bernardo Lloret-Fuentes</Company>
    <Product>ASP.NET Core 2.2 with Angular 7 Template</Product>
    <PackageId>ASP.NET Core 2.2 with Angular 7 Template</PackageId>
    <Description>ASP.NET Core 2.2 with Angular 7 Template</Description>
    <PackageProjectUrl>https://github.com/blfuentes/NETCore2_2_Angular7_Template</PackageProjectUrl>
    <RepositoryUrl>https://github.com/blfuentes/NETCore2_2_Angular7_Template</RepositoryUrl>
    <StartupObject>AppName.Program</StartupObject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.AspNetCore.SpaServices.Extensions" Version="3.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" Version="3.1.2" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.2" />
    <PackageReference Include="Microsoft.Extensions.Http" Version="3.1.2" />
    <PackageReference Include="Microsoft.Extensions.Options" Version="3.1.2" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.1.1" />
  </ItemGroup>

  <ItemGroup>
    <!-- Don't publish the SPA source files, but do show them in the project files list -->
    <Content Remove="$(SpaRoot)**" />
    <None Include="$(SpaRoot)**" Exclude="$(SpaRoot)node_modules\**" />
  </ItemGroup>

  <Target Name="DebugEnsureNodeEnv" BeforeTargets="Build" Condition=" '$(Configuration)' == 'Debug' And !Exists('$(SpaRoot)node_modules') ">
    <!-- Ensure Node.js is installed -->
    <Exec Command="node --version" ContinueOnError="true">
      <Output TaskParameter="ExitCode" PropertyName="ErrorCode" />
    </Exec>
    <Error Condition="'$(ErrorCode)' != '0'" Text="Node.js is required to build and run this project. To continue, please install Node.js from https://nodejs.org/, and then restart your command prompt or IDE." />
    <Message Importance="high" Text="Restoring dependencies using 'npm'. This may take several minutes..." />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm install" />
  </Target>

  <Target Name="PublishRunWebpack" AfterTargets="ComputeFilesToPublish">
    <!-- As part of publishing, ensure the JS resources are freshly built in production mode -->
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm install" />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm run build -- --prod" />
    <Exec WorkingDirectory="$(SpaRoot)" Command="npm run build:ssr -- --prod" Condition=" '$(BuildServerSideRenderer)' == 'true' " />

    <!-- Include the newly-built files in the publish output -->
    <ItemGroup>
      <DistFiles Include="$(SpaRoot)dist\**; $(SpaRoot)dist-server\**" />
      <DistFiles Include="$(SpaRoot)node_modules\**" Condition="'$(BuildServerSideRenderer)' == 'true'" />
      <ResolvedFileToPublish Include="@(DistFiles->'%(FullPath)')" Exclude="@(ResolvedFileToPublish)">
        <RelativePath>%(DistFiles.Identity)</RelativePath>
        <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
      </ResolvedFileToPublish>
    </ItemGroup>
  </Target>

  <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
    <TypeScriptTarget>ES2015</TypeScriptTarget>
    <TypeScriptJSXEmit>None</TypeScriptJSXEmit>
    <TypeScriptModuleKind>ES6</TypeScriptModuleKind>
    <TypeScriptCompileOnSaveEnabled>True</TypeScriptCompileOnSaveEnabled>
    <TypeScriptNoImplicitAny>False</TypeScriptNoImplicitAny>
    <TypeScriptRemoveComments>False</TypeScriptRemoveComments>
    <TypeScriptOutFile />
    <TypeScriptOutDir />
    <TypeScriptGeneratesDeclarations>False</TypeScriptGeneratesDeclarations>
    <TypeScriptNoEmitOnError>True</TypeScriptNoEmitOnError>
    <TypeScriptSourceMap>True</TypeScriptSourceMap>
    <TypeScriptMapRoot />
    <TypeScriptSourceRoot />
  </PropertyGroup>

  <ProjectExtensions><VisualStudio><UserProperties appsettings_1json__JsonSchema="" /></VisualStudio></ProjectExtensions>

</Project>

差分はこんな感じです

コンパイルして実行するとエラーが発生する

依存関係を解決できれば、コンパイルが通るようになります。

しかし、実行時にこのようなエラーが発生します。

Endpoint Routing does not support 'IApplicationBuilder.UseMvc(...)'. To use 'IApplicationBuilder.UseMvc' set 'MvcOptions.EnableEndpointRouting = false' inside 'ConfigureServices(...).

公式以降ガイドに従ってStartup.Configure()の中身を書き換えます。

ASP.NET Core 2.2から3.0への移行| Microsoft Docs

Before

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
    }
    app.UseRouting();

    app.UseHttpsRedirection();
    app.UseStaticFiles();
    app.UseSpaStaticFiles();

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller}/{action=Index}/{id?}");
    });

    app.UseSpa(spa =>
    {
        // To learn more about options for serving an Angular SPA from ASP.NET Core,
        // see https://go.microsoft.com/fwlink/?linkid=864501

        spa.Options.SourcePath = "ClientApp";

        if (env.IsDevelopment())
        {
            spa.UseAngularCliServer(npmScript: "start");
        }
    });
}

After

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Error");
        app.UseHsts();
    }
    app.UseRouting();

    app.UseHttpsRedirection();
    app.UseStaticFiles();
    app.UseSpaStaticFiles();

    app.UseEndpoints(routes =>
    {
        routes.MapControllerRoute("default", "controller=Home/{action=Index}/id");
    });

    app.UseSpa(spa =>
    {
        // To learn more about options for serving an Angular SPA from ASP.NET Core,
        // see https://go.microsoft.com/fwlink/?linkid=864501

        spa.Options.SourcePath = "ClientApp";

        if (env.IsDevelopment())
        {
            spa.UseAngularCliServer(npmScript: "start");
        }
    });
}

コンストラクターもIWebHostEnvironmentに置き換えてください。

差分はこんな感じ

UseUrlsの設定が反映されない

わたしの環境ではこれでUPDATEできました。
環境によっては依存関係で修正箇所があるかもしれませんので公式ガイドを参考にしてみてください。
ASP.NET Core 2.2から3.0への移行| Microsoft Docs