The previously working :disable_emails option in the BackupRestore.restore! function seems not to be passed to BackupRestore::Restorer::initialize any more:
while discourse/lib/backup_restore/restorer.rb at main · discourse/discourse · GitHub
def initialize(user_id:, filename:, factory:, disable_emails: true)
So now this option parameter is silently dropped, making it impossible to restore without disabling emails.
Maybe forgotten while refactoring, maybe removed on purpose?