(Laptop) Booting into Manjaro hangs when external monitor is connected

This seems most relevant:

So the issue is likely with the nvidia driver. I am no expert in that field, so i can only forward you to some documentation, maybe try another driver compatible with your model or the open-source nouveau driver.
https://wiki.archlinux.org/title/NVIDIA#Multiple_monitors
https://wiki.archlinux.org/title/NVIDIA/Troubleshooting


You might also want to try other kernel versions, like the newer 5.13 or the LTS 5.10.