I wish I had a answer other than moving to inmotionhosting.com
I just got off the phone with them and the salesman said php 7.x is still available till sometime in 2025.
But that answer was for today things may change.
They are a great host for UBB I have moved 3 UBBers to them with no complaints.
Option 2 is to beg your existing host to roll you back
Option 3 buy a renewal with UBB with agreement from the programmers first to install it for you since all that is left we are told is the installer/upgrader script.
