What firmware are you currently on?
I am pretty sure this is a firmware (2021.4.18.x) issue, I am assuming they did something with the firmware for 2021 OEM power trunk. I think there's a disconnect in power momentary on the trunk harness when you open it. I can confirm that I don't have any damage on my OEM trunk harness I tested the continuity on each wires. Hopefully this will be fixed on later firmware. According to
@JD_TM3 adding CANBUS fixes the black screen issue when opening trunk, so perhaps maybe you can order a CANBUS harness from hansshow?
If you want to go back to OEM, you would need to replace the struts and the trunk latch hook. I gotta say removing the hansshow struts (or EVOffer struts) isn't easy for the bottom part since you don't have any room to put flat head screw driver in, you'd need to find some kind of hook with flat end to pry it. Took me awhile to get it out and being very careful not to use too much force to open it so it doesn't hit the glass. Also depending on how your installer wired the struts you may have to drop the bumper.
Anyways, I replaced my hansshow power trunk to EVOffer(Tesla Offer) power trunk today and quite happy with it. I don't experience anymore black screen although there is black screen momentary when you open or close it but it doesn't cut off the power of the rear camera. Hoping it stays this way, and tesla fix their firmware for that short blackout.