https://www.thunderbird.net/en-US/mobile/
Thunderbird Mobile — Thunderbird
Thunderbird is a free email application that’s easy to set up and customize - and it’s loaded with great features!
thunderbird mobile
https://ftp.mozilla.org/pub/thunderbird-mobile/android/releases/9.0b2/
Directory Listing: /pub/thunderbird-mobile/android/releases/9.0b2/
directory listingthunderbird mobileandroid releasespub