Looks like this is still an idea:
Publish all Salesforce IP Ranges available via a JSON endpoint
https://ideas.salesforce.com/s/idea/a0B8W00000GdZ2GUAV/publish-all-salesforce-ip-ranges-available-via-a-json-endpoint
AWS publishes its current IP address ranges in JSON format. With this information, you can identify traffic from AWS. You can also use this information to allow or deny traffic to or from some AWS services.
https://docs.aws.amazon.com/vpc/latest/userguide/aws-ip-ranges.html
Script-thrown exception" error on HTTP callouts to AWS as of Spring ’22
https://trailhead.salesforce.com/trailblazer-community/feed/0D54V00007epy6b