The OAuth support won me over to FairEmail (https://email.faircode.eu/) as well. Was a long time K9 user over several Android releases, but I guess I'm getting impatient in my old age. This last time had no end of trouble getting things to work and finally gave FairEmail a try. OAuth support for all my accounts won me over immediately. Now if Thunderbird would only make the same effort for the desktop...
I made the exact same move for the same reasons a few weeks ago. The UI is a little... dense, but plenty featureful and made working with required oauth for my school Outlook email pretty easy.
