If this, or the vibe-coding ban upsets you, you're not the target demographic of Codeberg. It's not a big tent project looking to host all the code in the word, like Github is. It's for principled, quality, open source, community-first software. Look at the explore page to see what that means: https://codeberg.org/explore/repos?q=&only_show_relevant=tru...
The entire point of Forgejo, the git forge that Codeberg runs on as well, is that you can run your own very easily. I've stopped having private repos on Github completely in favor of my own Forgejo instance, and it's way smoother and nicer. Codeberg was never meant for private repos, but if I get around to starting a new floss project that I want to put out there, Codeberg would be a great option!
And sure, right now there is no cross-forge collaboration, so you need to have multiple accounts. But forge federation is planned, eventually you should be able to contribute to your friend's project from your instance. If you don't wanna wait, go look at https://tangled.org/ or something.