I know it's well outside the scope. I was hoping someone who has struggled with the ugprade might be able to provide some tips. I don't have a development server, and I'm not looking forward to another eight hour session trying to get it working.

BTW, I downloaded the system requirements page and got this:
Quote
System Requirements Not Met
The following system requirements were not met. Please contact your host for help.
The required PHP extension gd_info could not be found. Please ask your host to install this extension. Please see UBBDev Wiki: gd_info
Apparently there is no gd_info module offered in the REMI repository. (We're on AlmaLinux.) We're using ImageMagick, nto gd. Do I really need this extension?

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