If your Ubuntu 24.04 system (especially one that started as a server install) randomly suspends or goes to sleep even though it's supposed to be a headless server, you're not alone.
This seems to happen when a server installation gets partially or fully converted to a "desktop" environment at some point — even if you never intentionally installed a desktop. In my case, I installed Ubuntu Server 24.04 directly with balenaEtcher onto NVMe/SSD and I got this weird behavior (my N100 server was suspending after 15 minutes).
The Simple One-Liner Fix
Run this single command and the random suspensions stop immediately (and persist across reboots):
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.targetThat is it!