Bulk response.
Both CPU's in question are either an (Intel) LGA 1155 or 1150. They're definitely at or just over 10 years old at this point.
Neither will save the encryption key, regardless of how simple they are. When I try the "Test" feature in the KVM and Seamless Display, I receive the prompt to "Check that ____ mode is enabled on the secondary"....
Both machines are on a Private network. They're both on the same network and subnet. The only thing that I can't validate is that the encryption key is actually SAVING. Which appears to be the bottleneck.