Though mostly happy with Beowulf, compatibility with new stuff is crumbling, so I've bought a little Geekom A5 for a parallel install of the latest Devuan, allowing a change-over without killing what still gives internet connectivity.

Downloaded: devuan_excalibur_6.0.0_amd64_desktop.iso

$ sudo dd if=~/Downloads/devuan_excalibur_6.0.0_amd64_desktop.iso of=/dev/sda bs=512k

Plugged that into left front USB socket on the A5, powered up & tapped <delete>, to invoke the BIOS.

In the "Boot" menu, have selected:

"New UEFI OS Boot Option Policy":