Great to hear it runs well on the Deck!
For movement, you can use WASD, arrow keys or the numpad, including diagonals with W+D or numpad 7/9/1/3. Shift + movement lets you attack non-hostile NPCs. Space is wait, R is rest, Z is explore, E is interact, V is look, X is sneak, Q is potion and H is eat.
The hotbar uses 1–0, with Shift for the second row. When aiming, Tab cycles through targets, Enter fires and Esc cancels. For menus, Tab opens the screen selector, or you can use I for inventory, C for character, T for talents, J for journal, M for map, N to explore the current world map tile and B for crafting.
For now, you'll still need the mouse for some menus. I'd suggest mapping the trackpad to mouse input and right-click to a trigger, since right-click shows the available actions for most things.
I'm planning to release the next version next week with fully rebindable keys in Options → Controls and complete keyboard navigation, including menus, map inspection and aiming with movement keys. That should make setting up a Deck layout much easier!