Yes the engineers team updated with a long blog post on the development situation and explained that they “will also need to rewrite these apps to retire their technical debt”.
Hopefully the new Android version will be released this year but they never mentioned F-Droid
Blog: https://protonmail.com/blog/engineering-team-2021-update/
Keep in mind that it’s a proprietary app, with premium features… All the opposite of what Fediverse clients should be if you ask me