I’m just leaving a few notes FWIW. Probably with errors.
Client, where, language, license, how many developers
Foxy Droid: gitHub, Kotlin, GPL3, 2 contributors
F-Droid: gitLab, Java, GPL3, a bunch of contributors
Aurora Droid: gitLab, Java, GPL3, 1 contributor (?)
G-Droid: gitLab, Java, GPL3, 1 contributor (?)
M-Droid: gitHub, Javascript (React-Native & Redux), MIT, 2 contributors
There was a good, unanswered, comment/question previously on possible security issues.