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
Git forge?
Just git. Git command line.
It’s about as trivial as setting up an Apache server.
The anonymous users part is maybe two lines in a config file.
The features are almost entirely part of the front-end, which is entirely up to each individual end-user.
Do you have a web server? You’re already 95% of the way there. A workplace was mentioned in other replies, which likely means this infrastructure is already in place.
So no PRs. No Issues. No CI/CD. That doesn’t work for 99% of actively developed open source projects with >10 devs
I know project that is developed by 10.00000001 devs
The difficulty of sending patches or reporting issues to the Linux kernel is a feature for them, as it keeps less-experienced devs from wasting maintainer’s time with garbage requests. For most projects it’s a bug.