Here's Gitea's own comparison to GitHub's Actions: https://docs.gitea.com/usage/actions/comparison

Sure, it's not identical, and no one claims it is. I think it's defensibly like them, though.

Yes it is. It's not identical, but it is "like" it.

Most of my build config run on either platform (Gitea and Github) interchangeably.

We've run Gitea actions (and contributed here and there) for a couple of years, since-by-side with Github. We host in containers on the Gitea side so there are some marginal differences as to what can be run in a job, but our experience has been very positive.