Fologram for Rhino is compatible with Rhino 5 and 6. For Rhino 5, Service Release (SR) 12 and above is required. An evaluation version of Rhino 6 is available here.
I have both Rhino 5 and 6, and it installs for one but not the other.
Occasionally when installing Rhino 5 and 6 concurrently the Rhino Installer Engine may be unable to install plugins for both at the same time.
You should now be able run the Fologram for Rhino Installer (RHI) and install for both Rhino 5 and Rhino 6.