I like ProtonMail, but it's a shame that they provide latest app versions for Android quickly and constantly only via Google Play store – as someone who uses their Github Releases, I'm still locked in with v3.0.17 :sad_cat:
It's not to say they shouldn't, but for all their talk about being anti-Google and anti-big tech (and rightly so!), they still don't provide a libre version, and a stable APK release out of Google Play store
