Just for reference purposes, I just updated a server to php71, and Joomla and Wordpress run fine on it. The speed of loading is dramatically improved. Fortunately, UBBThreads is on a different server, so that can wait until the work is done.

The Stovebolt Geek
https://www.stovebolt.com/ubbthreads/ubbthreads.php

Server Information
UBB.threads Version 8.0.0
Release 20240826
Server OS Linux
Server Load 0.11
Web Server Apache/2.4.37
PHP Version 8.3.11
MYSQL Version 8.0.39
Database Size 1.82 GB