TMC429 VS SmartSpin2k

Ok this makes a lot more sense. Does the TMC429look like it will work for you? You have 4 connections to the driver chip to the motor. 2 connections from the driver to the Arduino, the Arduino just needs the connection from the marlin microcontroller. So the wiring should be 4 data on the Arduino, 2 going the TMC, then 6-8 to motors.

Edit: maybe this was it? https://github.com/doudar/SmartSpin2k I don't know what your enjoyment for DIY stuff is, but this is doable.

This can automate resistance adjustment - https://github.com/doudar/SmartSpin2k

It’s a device that goes on the knob of a spin bike and turns it into a smart trainer. The project is in its 4th year and 3rd hardware revision. We went from no pcb to a pcb that was a carrier board for dev kits to now a full custom pcb. It works great! https://github.com/doudar/SmartSpin2k

Schwinn IC4 is a good bike. I hear good things about the Echelon Connect Sport as well. Both can be turned into a smart trainer with a bit of DIY effort using a SmartSpin2K to control the resistance dial automatically. It's a fun little addon that improves the experience. Worked brilliantly for me since I've got a very small condo with no space to bring a bike upstairs and onto a trainer. The spin bike was way easier to dedicate the space to 100% of the time and my partner also gets to enjoy it

Check out https://github.com/doudar/SmartSpin2k and add automatic resistance to your spin bike. Everything you need to build your own, or a limited number of pre built kits are available!

If the recumbent has a knob-based resistance control like a spin bike, you can use a SmartSpin2K device: https://github.com/doudar/SmartSpin2k with power meter pedals. (There's also a retail competitor, IDK about patents and such, but I always favor the maker version.)