For what it's worth I've been using the Behringer XR18 18in/8out fairly
successfully.
There is a native version of the app, it connects over the network.
A lot can be controlled through osc and midi too.
I managed to find a used xtouch as well that has 9 motorized faders and a bunch of
controls, network, usb midi and din midi.
It's a bit lite on documentation but there's a large enough user base to usually
solve problems.
I'll have to dig around for the list of osc command somewhere.
The on board effects are ok two, so sometimes I send everything from the DAW onto usb
channels and mix in the XR itself.
Hope this helps!
John