Check a couple things before you rearrange the furniture.
When you installed FreedomBox on Debian did you also install a desktop environment? If so there is a support thread on this where Gnome was putting the FreedomBox to sleep.
If you did not install a desktop environment, check the service targets in Cockpit. Go to Services and select the Targets tab.
Here’s hibernate. Use the search field in the targets tab:
Here’s sleep:
You’ll want to “mask” these services if they are active so they don’t trigger. Here’s what Google says about that:
You can mask these from Cockpit using the three dots menu in the service target…
(my browser doesn’t render that very well - but there’s a menu with Start, Mask, Pin unit)
If that’s not it, then I’d hook up the keyboard and monitor and look if there are BIOS settings for this.