Follow normal install instructions. Reference this document for issues.
You let your installer drive touch a Windows machine. don't do that. reflash and try again.
Caused by conflict with the SeaGate BIOS. This isn't an issue with Qubes 4.0 apparently. Fix here.
You're installing on the wrong disk. Run lsblk
and find the top-level disk where Qubes is installed. For me, it was a disk starting with nvme
'cuz that was my hard drive yo.