While I do own a GitHub account, I was asked to sum up similar issues for GitLab and the like so here it goes:
Many projects are using GitLab, either gitlab.com or their own instance under certain circumstances.
Some issues on that topic:
It was supposed to be worked on for some releases but seems to have been many times postponed. This means many users, including me, are unable to contribue issues or MR on many FLOSS projects there. One exception to this, F-droid had the great idea to create an anynomous account with public creds they give to anyone asking for them on IRC. This still means someone else went though the reCAPTCHA, which makes it a last resort and not really a win.
Other projects surch as GNOME hosts their own GitLab but makes it difficult to sign up with respect to the users for the same reasons. I could create bug on their old bugzilla, I can’t anymore contribute since they moved to this gitlab, unfortunately.