If ForgeFed gets up & running you should be able to self-host your own compatible VCS repository & send pull/merge requests from it instead of needing to create an account then for & use up space on another’s forge. The Forgejo lineage has a strong interest in this technology. Currently the only decentralized+popular way to send patches is via email so this will help put the D back in distributed version control system (DVCS). This would not only be great for users getting to keep their private data, but the distributed nature adds a layer of resilience for downed Microsoft servers (happens often) or censorship/sancations as with even a little momentum, your project will have mirrors in multiple jurisdictions.
GitLab is open core, which is a step up from fully-closed, but isn’t fully open (nothing inherently wrong with that, but it is of note). The bigger issues with GitLab to me are twofold: 1) it’s slow built on Ruby & React (I think) where it can’t run on a potato requiring both excessive CPU as well as data usage while also requiring JavaScript & 2) GitLab is publicly traded which means there are shareholder requirements for them that can easily get in the way of what is good for users (or even what will be or continue to be licensed with a free software license).
Codeberg is ran by a German nonprofit which means they aren’t trying to put profits in the way of users, but also being in the EU, they will have strict requirements for user data which means it’s safer. As far as I can tell, there are no ads & it runs fast & works well enough without JavaScript. I would rather see more self-hosting personally, but if it isn’t practical for you, this is a good option. With it being built with Forgejo, it should in theory introduce a lot less friction migrating from Codeberg to self-hosted Forgejo in the future.
Forgejo isn’t without flaws tho. One of the goals of Gitea (forked from Gogs) vs. Forgejo (forked from Gitea) is trying to be more compatible with Microsoft GitHub even moving its continuous integration (CI) to Forgejo Action to be compatible with all the bugs & YAML spaghetti that MS GitHub uses. They copy the generally-bad pull request model too which only is optimal in certain uses cases, bottlenecking review & having a UI that leads maintainers more to commenting on how to fix something rather than saying “thanks”, merging, then fixing small nits themselves to not waste the contributor’s time in review if they just want a small bugfix, not to learn your entire codebase + style + process. By copying MS GitHub too closely, you can up being a clone that is just FOSS while risking having something that is technically differentiating which is ironically counter to inspiriting migration since while it might be easier, the benefits seem moot (maybe even just philosophical) instead of providing something users want to leave for (which is what I think you might be getting at). Additionally being Git-based as well means Forgejo (& others) are stuck with snapshots that factor in time & patch order causing unnecessary merge conflicts with multiple users which is solved by choosing a better version control system (VCS).
Gerrit is probably the poster child for branchless, stack-based diffs in Git. It takes some get getting used to, but once adjust your thruput is really ramps up. In some sense tho, this is a hack by tagging changelist values in the commit message to help reconstruct what the heck is going on due to Git limitations, but it’s old & robust enough to trust that system & many of its users absolutely swear by it (I have limited exposure but have used it more recently I can feel the appeal). You should be able to slap it in front of any Git server—even just straight host HTTP if not something lightweight like cgit, gitweb, or Ayllu. (Jujutsu is the same commit hackery in a different package & I don’t think it moves the needle as much as folks think being ultimately shackled to Git’s design decisions).
If you look outside of snapshot-based tools like Git, Mercurial, & so on, patch-theory-based options offer refuge. Darcs & Pijul are the leading (D)VCSs in the space. Darcs is very mature & shows its age in many ways (but is still developed & works good enough). Pijul is largely based on Darcs but meant be faster (& is), but it is immature; some features are missing on purpose to avoid the swell of Git commands, but I am personally surprised theres no good story for sending patches nor rebase. That said its identity system is how VCS should do it. Both VCSs have a lot less tooling built around them. Darcs is still supported by tools like Nix (but not Flakes) as well as Opam for OCaml with darcs hub & Smederee for maintained public forges. Pijul isn’t supported by much at all unfortunately & while Nest is a public forge, its lacking in features & basic usability like being able to fetch a tarball (despite
pijul archive). All the latter negativity may sound bad, but all tooling requires momentum. They would be prime candidates for the Gerrit workflow–just without the hacks needed. With the two being similar, I hope we see more tooling pop up to support them & just like trying a new paradigm of programming gives you insight on the ones you know, a new way to do VCS will teach you about version control. Do recommend.