By the way, we have an FAQ about K-9 Mail and Thunderbird for #Android that you might find interesting: https://blog.thunderbird.net/2022/06/faq-thunderbird-mobile-and-k-9-mail/
The Thunderbird Blog · Frequently Asked Questions: Thunderbird Mobile and K-9 MailAn evolving list of frequently asked questions about Thunderbird on Android, and K-9 Mail joining the Thunderbird family.