This was a lot of fun! I scored 700, I don't know if that's good or bad.
I feel like this idea would work really well with some puzzles where you have to work out how to kill yourself.
So it turns out the missing package wasn't what was causing the problem. From what I can make out from the crash logs Unity is crashing because of something to do with being unable to find URP shaders. But its getting late for me so I'm giving up on it for now, hopefully someone else will continue this for day 6.