https://blog.thunderbird.net/2024/06/thunderbird-for-android-k-9-mail-may-2024-progress-report/
Material 3 improvements, better developer documentation, and more in our May 2024 progress report for K-9 Mail / Thunderbird for Android.
I was excited (former regular thunderbird user in desktop mid/late-2000's to mid 2010's) and downloaded it but it appears to still use IMAP for email addresses on MS Exchange servers, so it's not an option for me at the moment, unfortunately.
Ah well. :(
I'm not a big fan of their new Material 3 theme. It's all very pink and orange and not enough contrast. Let's see where they'll take it.
They've got hardcoded colours in there still I think, because everything else on my system will be blue and then K9 is the only one that's pink.