Just to answer the first part about Roon compatibility: no single Linn device is Roon Ready and according to Linn they have no plans to do so.
Simple reason: to gain Roon Ready certification a vendors must license and implement Roon RAAT streaming protocol in his device. RAAT is closed source and Linn has a policy/dna/vision of only using open source. That prevents them to add Roon RAAT and other protocols (Airplay 2) to any DS device.
The reason your Linn works at all in Roon is because the Roonlabs devs implemented the Linn protocol (Openhome) inside the Roon software in order to gain compatibility with one of the (back then) major vendors of streamers.
While this is great, being not Roon Ready means that you will not be able to setup multiroom streaming between any Linn and any other Roon Ready device (using the Raat protocol).
I wanted to buy a Linn. But due to lack of Roon Ready and Airplay 2 I have decided against it. In my opinion Linn is absolutely great at hardware design but are failing with their software strategy.