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
They been doing this for years. Here is a GitLab forum post about it.
As a gitlab user myself, I prefer gitlab over anything else because of their CI/CD. The free compute units run instantly now, no more queues orwaiting. A couple years ago, my pipelines would timeout after 3 hours.
That post is only in regards to the CI feature. But today, even basic registration requires personal identification. You cannot even report bugs on open source projects without