I cannot get my Pi Cam 3 working

Welcome pspblink,
since nobody is replying, I’ll try.

I don’t use a camera.

My advice would be, try another forum (but I can’t guide you). My impression is, cameras are a little taboo here. They use a lot of capacity of the system, so they are not recommended. Have a look at the Magneto X with genuine Klipper Magneto X Magnetic FFF 3D Printer by Peopoly, which comes with a HD camera (does not help you, but it’s working).
I’m also thinking about installing a camera. I would reduce the frame rate and resolution to keep data traffic from the camera low.
What is your goal? Do you want to check your current print or do you want to post fancy videos of your print?
A big chunk of data from the camera might cause Klipper problems. I hope this helps you.