EDIT: A better version of migration can be found here: https://git.jonasfranz.software/JonasFranzDEV/gitea-github-migrator (not written by me) and it also migrates issues as well. Below text kept for archival sake but Jonas’ code is much better than mine so don’t use code below.
I’ve just posted a Gist of it with comments on github here: https://gist.github.com/techknowlogick/c2367e03baff9f16b3c5cc9d9a5d13ca
Note it is pretty untested, but I have been able to migrate > 300 repos from github to gitea with it so hopefully it’ll work for you too. In case your repos aren’t on github (as it sounds like they aren’t), then you can remove the github part of the script, and just put an array of your HTTP clone URLs and have the script loop over them instead.
Let me know if it doesn’t work, or if you need instructions on where to get tokens from for gitea, and I’d be glad to help.