I've played it for many years on a desktop computer with a mouse, but now play it directly on the Deck for the pick-up-and-play convenience. Controls took some getting used to, but it looks and plays very nicely.

OpenTTD.

I wanted something slim and light, so I got the Waterfield Magnetic Case (in all waxed canvas). Keep my Steam Deck in there any time I'm not using it.

OpenTTD.

Aren't all of these things basically out-of-band investments? They didn't recontribute upstream to these projects from what I understand

Maintaining a fork is not mutually exclusive with contributing changes upstream. Valve's policy is to upstream everything.