No boot, led 1 and 2 on, fan spinning

Greetings.

Someone brought me an iMac 21.5” - 2019 - which doesn’t chime and doesn’t boot. The fan spins normally when a screen is attached and - as expected - very loud without a display. There’s no hd nor sata cable. There’s a working ssd on the backside of the logic board: it works because I successfully mounted it on a different machine for testing. The screen is smashed and the chassis shows signs of a heavy impact. Only led 1 and 2 are on. Both leds light up as soon as the power cord is inserted. An external display remains black too. SMC reset did nothing, PRAM reset is impossible since the usb-keyboard is not active.

When I removed the screen, all stickers were in place (on lower left screw of logic board, all 4 screws on heatsink), showing that the logic board had not been removed before I did.

Can anyone help, please?