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 think having my real life phone number tied to a website or game account is a trivial ask. I'd like my data to be private, especially something as real-life and tangible as a fucking phone number. Sure, there are ways around these things, you can get a fake phone number for cheap (or possibly even free), but that's rather more effort than I'm willing to put in for most things. If I need to enter a phone number to sign up for an account for something, chances are very extremely good I'll just decide I don't need the account that badly. I don't think I'm alone in this.
Which means you likely weren't invested in engaging in a meaningful manner. That is especially important for filing a bug report on an open source project.
And I guess I just don't view a phone number as having much value from a privacy standpoint. Basically every number is compromised to the point that it is dependent on your phone/service provider to block spam. One more site having my phone number doesn't really bother me if it is a site I want to "engage" with.
Also: Never underestimate how much data is already out there just based on what pages you load. Privacy is long since dead and people do not understand how easy it is to cross reference to realize that "Jimmy in The Netherlands" is actually "Jim Stark at 101 Fake Street in Baltimore Maryland whose sister is Susie Clark with facebook username sclark_420"