It's slow, but so long as you don't do anything “out of the ordinary” (i.e. try to act like the average sort of person who would use Jira), it's decent enough to use. I've personally had no workflow issues, though I could tell there was something deeply wrong with the internals.

Then again, if you're only using the “ordinary” features, Jira doesn't have much advantage over any other bug tracker; Gitea can integrate with Jira just as well as with any other bug tracker, and well enough that the Jira / Confluence integration isn't necessary.

The Atlassian softwares are okay, but (from my limited experience) worse than their alternatives. On several occasions, I expected a bug, but it refreshed or redirected, and there wasn't a bug. I have found no bugs while using Jira, and not unusably many while using Confluence… but I can say the same for Gitea, GitHub, Gitlab and even Bugzilla. (Gitea's native issue tracker is actually good enough – and therefore better than Jira – for everything I ever used Jira for.)