Were the PSU cables re-used from the previous power supply?

Recipe for dead components if true.

It usually says right under the CPU heatsink, or right under the top pcie slot (under the GPU). I'm not seeing it under the CPU, so the GPU most likely needs to come out.

Would be nice to get a photo from under the GPU, commonly the mobo model names are written there. Other than that, what wattage is your friend's PSU rated for? Maybe the PSU just isn't powerful enough to run safely?

Another possibility could be that the CPU also got stolen, they should check under the cooler to see if the CPU is in place

Looks like an rog strix b450 f motherboard

can they temporarily remove the GPU to give you a better look at the lower half of the mainboard?

If you get a shot of the rear IO, you can probably determine what is is using the AM4 google sheet, though that'd be a bit long winded.

Without being able to see the model number label (usually not located far from the serial number label), it's really hard to tell. Also look where the peripherals are connected. Sometimes it's there.