I’m a little surprised to read this because Google Mail works fine for me in Firefox (ArchLinux). In fact it’s smoother than some of the Electron-based clients I’ve tried and less painful than trying to get push messages on Thunderbird working (sure, there is always IMAP but that requires regular fetches).
FIY, IMAP actually allows "push messages" via the IDLE extension. If you use K9 on android, it's enabled by default. I never used gmail, but I'd be surprised if the gmail imap server didn't support it (and I would dismiss gmail entirely if it didn't).
Is this a new thing? I don't recall seeing an option for that in Thunderbird (desktop version by the way; not the mobile / Android version) the last time I looked (~9 months ago).
I don't use Thunderbird myself - was just following the discussion on from the OP who did use it. However I've yet to find a client I like so genuinely interested in any suggestions you might have.
I'm currently using mutt with "getmail" (which does support IDLE), which I can recommend -- it's an excellent client, but only if you're fine with tweaking.
I used TB until two years ago, but I gave up with it's unfixed bugs and quirks. I do prefer graphical clients, but not if they are clunky or buggy.
I used Silpheed and Claws for years, but Silpheed locks (or used to lock) the UI during fetch (unacceptable IMHO) while Claws has some critical bugs in the filter/rule logic that made me lose mail in several occasions by refiling into the wrong folder while processing a lot of messages. If you arent't a heavy filter user you might be fine with it though, I think Claws gets a lot of things right.
KMail wasn't bad when I used it, but it was too long ago to make an honest comment today.
