I can recommend Jerboa on Android. Used it since the start and never had problems with it (and its lightweight).
Yeah it sucks but at least they have a good Linux AppImage (sadly no BSD). Their Android client is also fine and is on F-Droid.
I am using Tuta and am very happy with it. I like the feature where you can send encrypted Mails to anyone and theyβre unlocked via a password (i dont know if others have it). Important for me at least is, that theyβre based in germany.
I can recommend Jerboa on Android. Used it since the start and never had problems with it (and its lightweight).