I've bought Proton Mail. But I don't like the fact that I depend on their mobile app instead of being able to use K9-Mail and their proton-bridge on desktop to

I've bought Proton Mail. But I don't like the fact that I depend on their mobile app instead of being able to use K9-Mail and their proton-bridge on desktop to connect to Thunderbird. Also they don't allow you to initiate an email with "From:" begin an alias (like "me+somealias@mydomain.com", you can only use "me@mydomain.com") (workaround is doing it from Thunderbird). I even requested this as a feature but their Support rejected the proposal. Because of those I think I'll switch to something else (maybe Fastmail or Migadu) when my subscription ends in two years (I bought it with a 2 year discount and a sale).