I don't know that Openstack needs to go all in on GitHub. Gitea is great! Gerrit is a bit to get use too, signing up argh, it is disjointed, launchpad <-> opendev <-> gerrit and so on.
There are some good docs on how to onboard, but it's not "sign in with google" and off to the races. Also, if for reasons you had a launchpad account for decades ago, it's not straightforward to recover. (at least in my specific use case). Folks on IRC are keen and willing to help, so not a people thing.
If you are coming from an enterprise company, or even a smb/startup, that uses github, gitlab, bitbucket, the context switch is big, but not impossible. For sure there are some improvements that could be made, what is up for discussion no doubt, the gerrit oauth could help.
One thing I find a bit disjointed is that bugs are in launchpad, patches are in gerrit, code is in gitea. Previous comments have focused on the git review process in and of itself, which is fine, but made losing context on the wider UX for newcomers?
Openstack is a big project with a magnitude of moving parts.
Cheers
Michael