IMO the best choices are Tuta Mail or Proton Mail. Proton has the best UI and UX but is a bit controversial due to its CEO. I personally use Proton because the UI is that much better.
They have a bridge app that lets it work with Thunderbird, though I think you lose some functionality. I did this before they had the desktop app setup
@LavaPlanet@LEONARDE11 I switched a few times. With Tutanota. It's good and does what I need. I like it so much have gone from the free plan to the paid plan. My advice is if you're not sure, just switch.