Secure Boot is not implemented by Arch Linux on which EnOS is based.
It is subjected to much heated debates that pop up once in while.
Here is one recent example: Why doesn't EndeavourOS support Secure Boot out of the box?
Users could however implement it on their Arch systems but it involves some serious command line acrobatic. I wouldn’t dare myself!
https://wiki.archlinux.org/title/Unified_Extensible_Firmware_Interface/Secure_Boot
PS. I would give the solution to @pycrk since they spotted the cause.
After that it was a smooth ride 