I have created a cocoapods proxy repo in nexus 3.21.1 with the minimal configuration as sed in the documentation.
When I try to get it using the url provided by the repo (in this test: http://localhost:8081/repository/test-cocoa/), it returns a 404.
I tried it using a regular installation and docker images to test it in other versions (3.20.0, 3.19.0…)
Thanks for your message!
Direct access to a repository is used by client applications (a cocoapods client in this case) and GET request to the root of the repository should return an error message with an explanation. I created a ticket to fix the 404 error for the cocoapods.
To access repository in a browser try something like http://localhost:8081/#browse/browse:test-cocoa/ or something like http://localhost:8081/service/rest/repository/browse/test-cocoa/ to use HTML index.