I do not (and will not) use GitHub for my own projects, although I use it for viewing other projects that do use GitHub and for communicating with them. Mirroring projects on GitHub (and possibly other services too) even if the main working is not on GitHub, is also possible (I might add mirrors on GitHub and others in future, but currently I only have the main working hosted on my own computer and the mirror on Chisel, and I still intend to keep both of these even if there are mirrors on other services too). (Even SQLite is mirror on GitHub even though its main working is hosted by themself instead and is not even using git.)
I would not recommend using GitLab unless it is not the only mirror of your project (it is acceptable if you are mirroring it on something else, too). If you do want alternatives, you may consider Codeberg, NotABug, and/or Sourcehut. The reason I exclude GitLab is because it cannot display the files unless JavaScripts are enabled (or if you use the git protocol, which is kind of confusing compared with fossil) (it is OK if it uses JavaScript for other functions as long as the files can be viewed without it) (this is not a problem if there are other mirrors, since you can view the mirrors instead).
Collective action is hard, and it's even harder when billionaires make conscious, organized efforts to disrupt it.