I think that there's nothing stopping K9 from working with XOAUTH2/gmail, except that someone needs to put in the work. I implemented it a few years ago for a w

I think that there's nothing stopping K9 from working with XOAUTH2/gmail, except that someone needs to put in the work. I implemented it a few years ago for a webapp, and it's not so bad. I don't especially like XOAUTH2 as a system or that it's being enforced now, but it's entirely possible to be interoperate with XOAUTH2, and I don't see how it's "proprietary".