I have mixed feelings. He took the user interface design into a direction that almost nobody wanted and then he ignored all of the negative community feedback.

I have mixed feelings. He took the user interface design into a direction that almost nobody wanted and then he ignored all of the negative community feedback. If you go look at forum.k9mail.app threads, you can find hundreds, if not thousands, of posts with harsh feedback of the changes he introduced back in 2021 with what I think was the 6.0 release.