Omarchy OS: How do I check which services start at boot?

Use systemctl for system services and inspect your Omarchy session autostart file.

systemctl list-unit-files --state=enabled lists enabled system units; systemctl --user list-unit-files --state=enabled lists enabled user units. Omarchy session commands added by you are in ~/.config/hypr/autostart.lua. An enabled unit may still start only when triggered.

Source: Omarchy manual.