if using lxc the container.
you need to execute it with more priviledges
if you are already, or are using lxc the VM
your kernel needs to be ubuntu's -generic kernel rather than the -virtual kernel... -virtual doesn't have binfmt support in it the last time I checked.
misc building tips.. I personally hate the LIB_TAG thing.. and prefer to just force it to use whatever branch I'm using.. here's a hint for that https://docs.armbian.com/Developer-Guide_Build-Preparation/#using-alternate-armbian-builder-repos-and-branches
How to build from the kernel source you want and love armbian builder
As we mentioned. it's not that the armbian build checkout has changed the minor release. it's that the upstream has (it's a weakness we have). So you're going to want to specify your own kernel branch/commit/target etc by hand.
so in theory you should be able to create the file
font-family: Consolas,"courier new";
background-color: rgba(0, 0, 0, 0.2);