Hello @nyev and @Lalitk, I received my MU1!
I was able to deauthorize and unpower my Nucleus+ and start Roon Core on the Grimm fairly easily. Somehow I muddled through the confusing internal drive thing and do see the internal drive. Mine is 8T. I got Qobuz and Tidal started easily, and have moved some of my files to the internal drive.
BUT, I have so far failed at being able to restore my roon database from a backup. I have a bunch of playlists so I want to do this. I have found the instructions for this confusing.
SOUND: Amazing. I have my JCAT M12 switch upstairs feeding a 20m run of Supra Cat 8, into the MUON PRO filter, feeding the MU1. Then my K-S Elation AES into my Tambaqui. I am using a K-S Realization power cable. The music is so 'easy'. The Tambaqui has always been very resolving, yet now I seem to hear more things but in an unstressed way. The bass is also much fuller. It just makes me smile and I want (and have) stayed up very late listening to my favorites.
I removed the Muon Pro filter, but think it adds something. Not as big as an impact as before the MU1. I put it back in.
I also have a Network Acoustics Muon AES cable to compare. It is very good and costs less than its competition. It is a close second to the Elation.
I have also been streaming to three other endpoints now using Roon Core in the Grimm. It has worked perfectly.
Maybe everyone know this, but I was slow to realize that running additional Roon endpoints lessens the sound quality. When I sit down late at night, only running my main system, it always sounds amazing. I thought it was the time of day or power grid issues. But it is easily heard adding a second zone while critically listening.
A big thumbs up for the Grimm, but advice appreciated on restoring my Roon Database!