I switched to dockhand and it handles that nicely, including scanning for vulnerabilities in new images.

Same here, SimpleLogin via Proton Pass with my own domain (well a sub-domain of it anyway), works a treat!

Yes, you change your DNS settings so that your domain points to the new provider servers and recreate your email addresses there. You won’t have the old emails unless you backed them up and restored them but the address will be the same.