Would I need to do anything with the custom domain beyond registering it for this to work with an email provider?
Because this sounds like a great migration plan: set up a custom domain, add it to protonmail, update emails, export data, and then switch providers.
I’m just a bit clueless on the whole setting up a custom domain part.
Thanks! I registered a domain with cloudflare and that was easy enough. I’ll read up on some alternative providers and see how this all shakes out.