Oh man, I didn't even think about Single Sign On. Changing your email on every service you've ever interacted with is a huge project, but if you used SSO, a lot of those can't be changed to conventional emails, and even if you can pick up your domain and hop to Fastmail or something those are going to break.
I was already livid about this change but this is the piece de resistance. Holy hell. Even after migrating to a regular Google account I've still been using my custom domain as my identity.
