OS Name/Version: Ubuntu 20.04.3 LTS
Product Name/Version: AMP v126.96.36.199 running Minecraft Forge 1.12.2
Problem Description: I have a modded server that I made on a spare laptop for some friends and me, but I realized it's not going to sleep.
Actions taken to resolve so far: "Enable Sleep Mode" is on, sleep mode delay is set to five minutes, and doze delay is set to two minutes. I tried to do a vanilla server also in 1.12.2 and it did the same thing. When I attempted to force it to sleep, it made a little bump in the cpu usage and continued on as if nothing happened. (Note, here I changed the sleep mode delay to one minute and restarted the server for testing purposes.)
Possible useful information: This happens even when nobody has joined or attempted to join the server. I am running JDK 8