EQ APO doesn't support ASIO directly, and is therefore not bit-perfect, and therefore lossy.
and yeah ASIO Bridge is limited to 8 channels.
I know that ASIO4All will wrap a sound device as an ASIO in/out device, but that won't help in the case of EQ APO as it doesn't do ASIO.
Jack audio can do 256 channels, and inter-app audio and ASIO. You may be able to go from APO to Jack to your sound device.
In my case I'm going from ASIO In to an app with dsp to ASIO Out, and in that case the middle piece, Audition, works great...
If at any point Motu has a firmware that can do full DSP onboard (instead of the half baked DSP it has now), then I'd be able to cut out the computer and Audition altogether, but until then...
Both the Motu ASIO drivers and Audition in ASIO mode are bit-perfect, and audition's SNR for DSP effects is better than -180db, so it's entirely hardware limited by the Sabre DAC (which has sufficient, if not excellent SNR as-is).
Adobe releases a new major release once a year in October, with patches in between, so every year my DSP gets more features added to it.
For example I can easily add a reverb phantom up-mix from the sides and rears so that my heights are "always on", and then save that as a multi-track file, and then also create another file with discrete Atmos heights for when I'm watching an Atmos disc.
Once Sandboxie 1809 comes out I can use that to host multiple instances of Audition, which is how I get around it's inherent lack of multi-threading. I found that one instance for each LCR, and then another for the sides/backs and another for the heights, and another few instances for the subwoofers seems to be an ideal load for a multi-core CPU. Windows figures out how to balance the load across all the cores. The Motu drivers are multi-client so every instance sees all of the available channels for routing any number of inputs to any number of outputs, therefore you're not limited in the routing department.
USB3 and ThunderBolt maxes out at 128x128 channels on the Motu's, so if you need beyond that, then you'd need multiple DSP computers and multiple AVB hubs and multiple 624's etc...
I don't see too many people needing such a rig, perhaps Beyonce on a world-tour or something LOL!
My current rig is 24x48 so I'm well under the Motu driver limit.
That gives me Atmos 17.1.6 or 19.1.4 or 18.2.4 or 7.2.15 or 7.13.4 overkill no matter how you align the dots. LOL
The driver limit per computer is 44.42.42, but you'd need a 64core AMD cpu to process that load FOR SURE!