After mounting, mount point doesn't exist?

[pebcak]

If your purpose is to chroot into your system and reinstall the Grub bootloader or perform other maintenance tasks, it is enough to use:
arch-chroot:

sudo arch-chroot /mnt

@TheSushiBoy

[liveuser@eos-2022.06.23 ~]$ sudo mount --bind /dev/mnt/dev mount: /dev/mnt/dev: mount point does not exist. dmesg(1) may have more information after failed mount system call.

You need to have a space between /dev and /mnt/dev.

You have also still an open thread about the same issue here:

UEFI or Legacy for 2x boot(win10)w/grub

Starting from fresh install on a 2015 Inspiron Dell. Goal is dual boot with grub bootloader, win10+En. I’ve tried doing this so many times and ran into all sorts of problems, so I want to restart from the beginning. I had read somewhere that I need to install using UEFI, but I can’t get the bios to read a usb if I do. Can I do Legacy, secure boot?

So actually no need to start a new one.