He must go to his own private servers hosting it, with powerful storage, bandwidth and backup.
Then I think it’s only DNS service to be f’d with by the enemy.
Private hosting is very expensive compared to cloud. Cloud offers scale that just isn’t possible in a private datacenter without a substantial amount of capital. Parler is too new. Of all of the cloud platforms, Amazon and Google wouldn’t have been my first choice, but Amazon is the best known by most technical resources and developers.