I set this server up (we're on dedicated hosting), and I don't believe I configured any cache on the server, but I'll check. I only run apache. Don't want to learn yet another app.

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

Server Information
UBB.threads Version 7.7.5
Release 20201027
Server OS Linux
Server Load 0.16
Web Server Apache/2.4.6
PHP Version 7.4.33
MYSQL Version 5.7.43
Database Size 1.85 GB