Just dropping this here in case anyone else hits it:
Backlight doesn’t work on a DV6-6180us, but adding:
acpi_backlight=native
to GRUB_CMDLINE_LINUX_DEFAULT and then
sudo grub-mkconfig -o /boot/grub/grub.cfg
resolved it
Vendor, etc. don’t work but native was the trick. Leaving this here for anyone else who’s decided to load up EndeavourOS on an old (MBR boot) laptop to get some more life out of it as a spare thin client or light media/gaming setup