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 https://forgeperf.org 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).