If you already have a custom email domain (which is a good idea for the usual portability reasons) _and_ you pick an email provider that supports 'catch-all mailboxes', you can make it entirely frictionless.

When I sign up for a new service, I register on the spot as e.g. [email protected], the mails they send are considered as a 'mistaken sender' and are sent to the catch-all mailbox (which is just my regular mailbox!)