The owner has went outside of the norm due to the severity of SnailGames colossal snafu and has updated the panel to allow ARK to toggle from the official ARK Release to the beta branch that rolls back to pre-Aquatica.

To access the setting, simply stop your server. Go to the basic tab, change the branch and restart your server. 

It -may- require a second reboot, and keep in mind you might find your mods broken in the future if you don't toggle back to the default branch once ARK fixes it and modders begin to uodate their work.