I think I have a pretty good idea of the options, but I want to check whether I’m missing anything.
Obviously, up to 32 channels are supported via USB (in and out).
It sounds like a Dante interface card is the simplest option for recording up to 64 channels, though somewhat pricey. With the interface card plus Virtual Sound Card software, I should be able to record (and send) up to 64 channels. As a bonus, this even works over regular ethernet.
The Waves interface card also seems to be an option, but I believe that requires additional hardware beyond the (also pricey) card. I’m not really familiar with the Waves ecosystem.
Am I missing anything? If not, I’ll just add a plug to say that it would be great to have an option to interface gigaACE/GX directly with a computer. (Or just a USB3 port, which should easily be able to handle 128 channels in/out at 96kHz.)