I haven't needed to contact support, but I think they have a manned tech support email address too.
Just get a domain like `Smith.com` and then use the email `John@Smith.com`. Then it doesn't matter if you're using Gmail, Fastmail, Protonmail, etc. You can switch to a different company whenever you want (to get the best rate, avoid abusive terms, bad service, etc) without having to update your business cards, websites, online accounts, etc.
You'll still need to have a way to back up your old messages though.
I used gmail with a custom domain for years before I finally decided to move to fastmail, which made the move pretty painless. That said, when I set it up gsuite with a custom domain was free. I don't think thats the case any more.