CentOS

Can anyone please explain to me why when I make changes to /etc/default/grub (I removed some blacklist nouveau entries and nvidia stuff), then after I've run...
...and reboot, then 'e' (edit) the CentOS entry, that "rd.driver.blacklist-nouveau modprobe.blacklist=nouveau nvidia-drm.modeset=1" are still present in the "linux ($root)/vmlinuz-4.18<etc>" line?

or ever better, how do I fix it? Thanks tons folks!

Is your system in UEFI mode? Does /sys/firmware/efi exist?

I am in UEFI mode, and /sys/firmware/efi does exist.

I have a dual boot setup - win10 and Centos 8.3 (up to date). I have been messing around trying to get Nvidia drivers installed, so I installed, then uninstalled some packages, not sure if in uninstalling the Nvidia drivers (both elrepo rpmfusion approaches) that something didn't get cleanly uninstalled. (if that's any help).

Thanks Trevor.

Hey Trevor - thanks for your time so far, I managed to get things "back to normal" by ... I have no idea what got updated that fixed my issues, but the system boots up with a normal set of arguments to the linux line via the grub boot menu.

Thanks again. J.

Note: CentOS 8 does use BootLoaderSpec https://systemd.io/BOOT_LOADER_SPECIFICATION/

You can set variables in /etc/default/grub and grub2-mkconfig will write /boot/efi/EFI/centos/grub.cfg for you.
Perhaps even update /boot/efi/EFI/centos/grubenv

However, the BLS has the "real" entries in /boot/loader/entries
(Re)installing kernel runs also 'grubby', which updates those.
Or something like that.