So it looks like @protonprivacy made their Proton Mail app proprietary – or do I miss something? On the PlayStore there's a v4.0.6, while the Github repo at https://github.com/ProtonMail/proton-mail-android didn't see any commit since last October, and has v3.0.17 as latest release.
I hope I'm wrong here and just missed a note that you moved the repo to e.g. Codeberg or so?