I play almost exclusively on PC, and even there controls are pretty standardized. WASD movement, E typically to interact. R to reload (if relevant). Space to jump.

There’s no analogue to the steam controllers touchpad anywhere. What do I do with it? How do I use the back buttons effectively?

It’s all doable to learn of course, but it’s just a slightly too high barrier for most. I’ve got a steamdeck and honestly I never use the touchpads or the gyro, they just feel awkward so I stick with a mostly Xbox style setup.