Kinda but not quite:

Costasiella kuroshimae are capable of a physiological process called kleptoplasty, in which they retain the chloroplasts from the algae they feed on. Absorbing the chloroplasts from algae then enables them to indirectly perform photosynthesis.[6]

Source: Costasiella kuroshimae

Apparently it’s a metadata bug, K9 shouldn’t be listed as Thunderbird. See comments ITT.

Yes.

Hot tip. You can enable ‘Install extension from file’ in mobile Firefox apps (Firefox, Fennec, Mull etc) by going to Settings > About Firefox (or About Fennec etc) > Tapping the name 5 times.

You should see a message about debug mode being enabled and the ‘Install extention from file’ option should be in the Advanced section of your brower settings.

In F-Droid (not sure about Play or other app stores) K9 v8.0 (and above I guess) is now listed as Thunderbird Beta for Testers. I and possibly others thought that the K9 version of the app would keep it’s branding all the way through, including it’s listing name or title in various app stores. Perhaps it wont or perhaps it’s a listing error. We’ll see.

FYI this is from 2022 but is relevant because Thunderbird (and K9 v8) just landed in F-Droid (and other android package managers I guess but I haven’t checked).

The process of importing from K9 Mail worked without issue for me. There is also the option to import from desktop using a QR scanner (or some kind of scanner, again I didn’t go down that rabbit hole).