I've had a personal e-mail ID on a custom domain for a long time that I've connected to everything from self-hosted setups to several providers including GMail. The web UIs have never been an issue thanks to Thunderbird.
Last year, I switched to ProtonMail (Thunderbird on Linux with their "bridge" client). Works flawlessly, spam classification works well alongside Thunderbird's junk classification, and the mobile app is pretty slick too.
Anecdotal experience being, a local client like Thunderbird (mine still has e-mails from 18+ years ago) + whatever provider via IMAP/POP has been a rock solid setup that has withstood time. It might not be wise to trust any cloud e-mail provider in the long run.