Its a generic Armbian Focal issue. This package is served from our repository, but it was simply never added there - for Focal, while it exits for Bionic. Its fixed, but it will take several days before it shows up since we are right in the middle of a major update ... A quick hack would be to edit /etc/apt/sources.list.d/armbian.list and change focal for bionic, update, install this package, change back to focal and run update again.
