Yes, it does seem, they are…
Entering the 4-th year on waiting for that “open-source release really soon now we promise” that they said back in 2015…
Never. They are just saying things which they will never do.
It means you can’t trust this service. Use other mail provider like cock.li
cock.li itself is not fully what one wants it to be. The owner itself states so on the website.
Will protonmail be available in F-Droid? Anyone working on it?
Not sure what you mean, Protonmail is not open-source, at this moment, so no.
This year or so