If you lose access to an Apple private relay or "hide my email" account and need to update your email to a new one, follow the steps below.
Change your forwarding address
On your iPhone, open the Settings app, then tap [your name].
Tap iCloud.
Scroll down to the iCloud+ Features section, then tap Hide My Email.
Scroll down and tap Forward To.
Select the email address associated with your Apple Account that you want to use.
This applies to email from all apps and developers using Hide My Email.