Search HDMI Multichannel using the magnifying glass search icon to the top right. You will find reference to devices such as Raspberry Pi or NUC which have Ethernet inputs, HDMI Outputs and run Roon Bridge.
There are several ways to play multichannel with Roon, for example:
Multichannel AVR/prepro connected with HDMI to a PC with Roon Bridge installed that will speak with your Roon Core (like your SonicTransporter) over the network
Multichannel DAC connected with USB to a PC with Roon Bridge installed that will speak with your Roon Core over the network
All-in-one PC with Roon Core connected directly to a Multichannel AVR/prepro over HDMI
All-in-one PC with Roon Core connected directly to a Multichannel DAC over USB
Multichannel network attached RoonReady endpoint that has a built in multichannel DAC or can be connected to one - aren’t many there but an example would be Merging NADAC and I think also exaSound Playpoint + e38
In my opinion from your description of your setup I would recommend option #1 which will translate to -
SonicTransporter --> network --> NUC/Pi/Laptop/etc installed with Windows and RoonBridge --> HDMI to Casablanca
What do you mean by “dedicated HDMI endpoint” ? Most devices with HDMI output also have other outputs.
Roon Bridge has all that is necessary for a device to function as a Roon Output. Roon has no additional Output functionality that is not present in Roon Bridge.
There are a range of devices with HDMI outputs across many price points, starting with Raspberry Pi or Allo Sparky SBCs running DietPi or RoPieee through NUC devices running Windows or Linux (including ROCK, if you wanted a Core as well) to more conventional computers like laptops. If it’s got an HDMI port and runs an OS that supports Roon Bridge then in theory it ought to work. But there have been glitches, hence the desirability of searching other users experiences.
If you want multichannel audio using HDMI, the only real option is a PC. You can connect a PC using Roon Bridge or have your Roon Core Pc connected to your AVR. I do both, using a silent NUC running ROCK and another silent PC in another location running Windows.
Just for the record in case somebody searches for HDMI: Lumin does not support multichannel, but our Roon Ready Lumin T1 / A1 / S1 has an HDMI output that supports 2-channel PCM 24/192 and native DSD64 (not DoP) via a dedicated HDMI hardware chip. (We also support DoP64 output to SPDIF.)