Thanks.

Just checked. Secure Boot is not enabled on any of my machines, which are Linux-only. Whew!

(I wonder if any of the ASUS subnotebooks I bought off eBay for minor embedded stuff have this problem. Have to power them up.)

My ASUS laptop had it enabled. I had to disable it as there just wasn't enough non volital memory to hold all the updates even after remove several EFI entries and resetting the BIOS. All my mini-PC's updated fine however. My Linux Protectli routers already had it disabled thankfully. They use Coreboot, unsure if that was a factor.