The Apple Mail client works very well with Gmail. The only real negative is that it’s not true push email, though it is largely close enough.

The thing I miss most about macOS now that I’ve gone all-in on Linux is actually Apple Mail. It’s just a simple and clean Mail app.

My current choice is Evolution and I’ve had very good luck with it so far. But ultimately the best Mail experience is on my iPhone.

I was using Thunderbird/BetterBird, but now that a Windows client isn’t a requirement for me anymore, I much prefer Evolution. Thunderbird is a notable pain when it comes to an inability to reliably export/import your user profile to other machines. It’s also such a cluttered application and I find the calendar UI to be horrendous. Good luck using a trackpad to scroll through months of the year.