I did it that last month, not because I have any expectations of privacy (I wish we could move away from emails entirely), but because I don't want to be so much at the mercy of what google decides, especially with their recent push on id verification left and right, and ties to this dystopian government. I'm gradually moving away from other of their products too.

If I was browsing options today, I'd also look into calendar and contact management / importing. Proton makes it easy to import existing calendars and they are kept in sync. They're still improving the calendar features though, so maybe you'll miss a thing or two there. Contacts are also easy to import, but there's no feature to keep them in sync with what google has, if you need a transition period. There is a merging/deduplication feature though.

And if you're using google workspaces, I couldn't figure out how to send an email from proton using the work domain, so that's something I still need to use the gmail web client or e.g. thunderbird.