I use Mailspring. The only thing missing from Mailspring for me is seeing what folders my emails are in when I run a search. Otherwise, it's the only non-CLI client I've found that let's me use the keyboard to select multiple emails and move them to a folder, something I do in Gmail.
If anyone knows of others, let me know! I've tried Claws, Evolution, Geary, KMail, and Thunderbird in addition to Mutt and aerc in hopes of finding something to replace Gmail.
To be fair, the first time I tried running local AI (and it actually worked), I was so surprised that I actually unplugged my Ethernet and tried again. I'm still surprised, but it's possible for the massive amounts of training data to be compressed to a model under only 10 or 20 GB.