My iMac won’t run Roon 2.0, it apparently will only run 1.8 legacy. The iMac is from mid 2011, but has upgraded hardware from about 2 years ago. So when I try to connect the two, it says “Roon is trying to connect but your core and remote are running two different versions.” Roon works fine with other remotes, new iPhone etc, but this is the biggest screen I have on the iMac and it’s my main desktop computer.
Roon 2.0 requires macOS 10.15 (Catalina) or later…
… If your Core or desktop remote(s) do not meet this minimum specification, they will be unable to run Roon 2.0.
If you are unable to update your iMac to run a version of MacOS that is at least Catalina 10.15 or later, then if you want to continue using it with Roon, you will have to downgrade your Nucleus, your other remotes and your iPhone to 1.8 Legacy to match the 1.8 Legacy running on the iMac.
Steps to do this, and the file that you need to install on your Nucleus, are given in this article: