I have a LG Gram 17 and I just now install Proxmox with a sd.
You must hold down F10 when LG logo pops up.
I downloaded Proxmox VE 7.0 ISO Installer and then I used balenaEtcher to install the image on my SD card/or (usb drive ) this is what i had at the time, so i can install proxmox on a usb...