Hi Pieter,
I needed to test my theme under Linux, so I decided to see if I could get this working as well. I'm not 100% if this is what you are looking for, but I followed step 3 "Create The Persistent Xubuntu USB Drive Using Universal USB Installer" form here:
https://www.lifewire.com/create-lightweight-xubuntu-linux-usb-2202083I used xubuntu-18.04-desktop-amd64.iso with the Universal USB Installer and setup a 4GB casper-rw file. My grub.cfg looks like this:
set timeout=1
menuentry "RetroFE" {
set gfxpayload=keep
linux /casper/vmlinuz file=/cdrom/preseed/xubuntu.seed cdrom-detect/try-usb=true noprompt floppy.allowed_drive_mask=0 ignore_uuid boot=casper quiet splash persistent ---
initrd /casper/initrd.lz
}
After getting the bootable USB going, I installed the dependencies listed in the documentation for RetroFE. The Linux binary from the current RetroFE download worked like a charm.
Hope this is helpful. Thanks!