Revealed: Our Plans For Thunderbird On Android
https://blog.thunderbird.net/2022/06/revealed-thunderbird-on-android-plans-k9/

K-9 Mail Joins The Thunderbird Family
To that end, we’re thrilled to announce that today, K-9 Mail officially joins the Thunderbird family. And cketti has already joined the full-time Thunderbird staff, bringing along his valuable expertise and experience with mobile platforms.

Ultimately, K-9 Mail will transform into Thunderbird on Android.

Thunderbird Alternatives for Android
https://alternativeto.net/software/mozilla-thunderbird/?platform=android