In order to change where apt or apt-get pull the openhd packages (to test a custom package for instance) you might want to alter the package-repo path in: /etc/apt/sources.list.d/openhd-2-0.list
The default for 2.0.8 is:
Nano to the package list file and modify to the list you want. For Example "openhd-2-0-testing.list"
To clear out old key and avoiding the error associated with an unsigned repo… get the error key by doing sudo apt-get update
sudo gpg --keyserver dl.cloudsmith.io --recv-key F856E94C65F425D6
Then
sudo apt-get upgrade openhd