I can’t help you as I don’t have any experience using Oauth2 myself.
Hopefully someone with some insight will jump in.
If you haven’t already done so, you may want to cross-post this question in the osTicket forum. There is absolutely nothing about this question that is actually osTicket Awesome specific. So you’re only going to get a small fraction of the eyeballs over here that you would there. ๐
Good luck!