If your IP (and possible your browser) looks “suspicious” or has been used by other users before, you need to add additional information for registration on gitlab.com, which includes your mobile phone number and possibly credit card information. Since it is not possible to contribute or even report issues on open source projects without doing so, I do not think any open source project should use this service until they change that.
Screenshot: https://i.ibb.co/XsfcfHf/gitlab.png
I don’t use codeberg much, but I have my own instance of Forgejo so I’m using the same software. My experience is that it’s really nice. The feeling is one of having what you need and no bloat.