This command in Debian/Ubuntu/Mint will get everything need installed for most Java based KVM viewers:
sudo apt install icedtea-netx
The following additional packages will be installed:
ca-certificates-java icedtea-netx-common openjdk-8-jre openjdk-8-jre-headless
It seems every other updated version of Java or Icedtea breaks things and I will save the frustration of Java for another post.........