Something keeps waking my screen back up

After a few minutes of inactivity, my screen switches off (as it should), but around a minute later, it switches back on again, for no reason - no one’s even at the desk.

This started happening after I put a new motherboard in (same installation of EndeavourOS, I didn’t touch the hard drive).

I’ve got a USB Wireless keyboard and mouse, so I unplugged both to check it wasn’t them, but the problem still happened.

I’ve checked the journal just after it woke the screen up, but nothing I can see

cat /sys/kernel/debug/wakeup_sources gives the only source ever responsible for wake-ups as hidpp_battery_0. the number went up from 26 to 28 after I did nothing but wait (for the usual wake-up for no reason), so I figure this just be the cause. But this is a mains desktop PC, it doesn’t even have a battery (apart from the little one that keeps time I suppose).