They just freeze the system if I try to open them from the file explorer.
I've not seen anything like this before.
Try `pv /dev/nvme0n1 > /dev/null` (or just cat, but pv will give you a nice progress bar if you install it). If that errors out or your machine freezes, you have a storage problem and probably need to replace your SSD. If that works, try booting in single user mode or from a USB boot drive and running fsck.
You can also try SSHing in from another machine while trying to open the file locally. If the SSH session dies instantly, it's probably a kernel panic. If it survives, you can look at logs and top see what happened (maybe the issue is the desktop environment locks up?)
Sleep issues, the dock stuff, those sound like legitimate driver/support issues that would affect anyone. But opening PDFs crashing your machine really sounds like either your hardware or install is specifically broken and needs fixing, or you're running into a really weird bug that is not hardware-specific.
I do, and this enables me to delete and reinstall any Linux version without changing my home directory.
It seems reinstalling the operating system is the first thing you should try.
I mean... Kind of? It's pretty clear that they're driver issues. Hardware manufacturers have to make in-roads with OS teams to get these things delivered flawlessly, otherwise they have to wait for the community to build fixes. System76 and Lenovo do their best to get ahead of driver issues from what I've seen. I'm assuming a lot of this has to do with the fact that OP is running 21.10 rather than an LTS release.