After further consideration, I decided not to try the docker solution. It's partly because I don't want to become a Linux software architect in my limited spare time. It's mostly because JRiver shouldn't make me resort to such nonsense.
I moved away from the PC-based approach over DLNA and back to my NAS-mounted JRiver install (QNAP) that allows direct, BIT-PERFECT, NAS-to-receiver data transmission via HDMI (including seamless HD video). (I wish support for this would resume!!) People, isn't the audiophile-grade processing and bit-perfect output the primary reason we like JRiver (in addition to the file management and Views personalization capabilities)?
As I mentioned in my original post above, the file editing challenges between client and server are just infuriating. I agreed with many of the suggestions in this thread, having been a JRiver user for over 10 years who has struggled through arcane software requirements so many times:
https://yabb.jriver.com/interact/index.php?topic=119241.0Riffing on the above thread, not being computer scientist, I have literally spent days of my life in aggregate battling through JRiver configuration challenges. Love the product concept, but have never loved the product execution. Once configured, it's amazing, but I can see 95% of people just giving up. It's a chore and it doesn't just work like so many modern competitors.
Please simplify the UX. Think focus groups, user testing environments...
We want the best for you (and us).