I switched from Thunderbird to Gnome Evolution several months ago. It's been great. Currently running latest flatpak on Debian Trixie with Gnome v48.
I do have one annoying niggle though...
I get a daily email from bringatrailer.com. It's basically a large-ish email of all the current auctions and it has a photo of each of the vehicles in the email. It can be a hundred or more images, lots of HTML.
I don't know if it is my slow internet connection (10Mbps) or if it is an issue with Evolution, but most of the time the email doesn't load all the images. It loads most images, but invariably not all. Re-opening the email makes it load all the images most of the time.
Thunderbird was always successful on the same internet connection.
So, I'm conflicted about whether I should open a ticket about this. On the one hand it is kind of a niche payload, on the other it should just work, and other clients handle it properly, or maybe it's some kind of lazy-load thing in Evolution giving up too early... I dunno.