Instead of "moving", let's at least have some mirrors up. Mirror all your repos to CB, make a FOSS tool to do this automagically for you. Let users be able to just click a button and boom, mirror.
The goal is to get at least a % available on CB, then we can think about where the community is
Why didn't codeberg make this FOSS tool though? Seems natural they should.
They disabled the mirrors feature because they didn't want a bunch of accounts mirroring large repos and doing nothing else.
Forgejo does support mirrors, just not codeberg.