The solution for me turned out to be unrelated to the game itself. I was playing on the Steam platform and apparently Valve had recently pushed out a change to the Steam client that broke controller support for Subnautica. The fix was to request acc…
Update: So Steam support gave me the option of joining the current Client Beta. Once the client updated to the Beta version I reconfigured Subnautica to use my trusty Steam Controller. It totally works now, just like before. And the Controller me…