Brave browserはサポートされていない

• Can't login to Trailblazer with Brave browser

https://help.salesforce.com/s/articleView?id=sf.getstart_browsers_sfx.htm&type=5

Brave isn't supported, use Chrome, Edge or Firefox on Windows. Safari on Mac.

You can use Brave, but when you run into issues you can't expect Salesforce to provide any assistance, they'll insist you use a supported browser.

It's a good idea to be comfortable in multiple browsers with Salesforce anyway. Some extensions on Chrome are pretty good and Firefox is a good alternative. Edge is getting better and is now based on chromium so better than older MS browsers.

https://www.reddit.com/r/salesforce/comments/17mciuq/salesforce_having_problems_with_brave/

Braveブラウザ　は対応していない

• I cannot add roles in the trailhead.

I don't think Brave Browser supports it.
Try using google chrome or safari

Supported Browsers and Devices for Lightning Experience
https://help.salesforce.com/s/articleView?id=release-notes.getstart_browsers_sfx.htm&release=244&type=5