I'm thinking of doing this and I haven't yet figured out how to migrate all the accounts I have associated with my GMail account. Do you have any suggestion/tips for a fellow potential immigratnt? :)
I moved to Tutanota and what I did is forward all my Gmail emails to my Tutanota email. It made it much easier to switch because I could immediately start using Tutanota and then migrate my accounts overtime to eventually delete Google completely.