the latest versions of porting lib are supposed to be for Minecraft 1.20.1 through 1.20.4, but when I use one of them in a 1.20.2 fabric workspace, it doesn't launch and says Porting Lib requires Minecraft 1.20.1

the supported versions listed on modrinth are messed up. Porting lib is tightly linked to MC versions.
Only 1.20.1 and 1.20.4 are supported, but no versions for 1.20.4 have been released yet.

1.20.2 isn't supported

Thanks for the clarification.