The perfect email client...so tough. I tried Mailspring but do not like having to create an account to use full functionality. It does look sharp but had issues with one of my accounts - proton. The mailbridge worked fine but emails would appear/disappear.
I tried Geary, Evolution, Kmail...others...to include Mutt but I just do not have the time for that one although conceptually, cool.
20 years or so later, I'm back 100% with Thunderbird. Love the combined inboxes and the ability to mod as needed/desired. Not as sexy as Mailspring but has everything I need, is reliable, and just gets it done. I do have the Tuta AppImage on the side.