I was able to do some Steam Deck testing this weekend. I'm sorry to say that Steam Deck is not a recommended Hadean Lands experience right now.
The problem is the on-screen keyboard. It wants to pop up and obscure the lower half of the text window -- which makes it hard to play. You could manually open and close the keyboard every turn, but that's no fun. Anyhow, the keyboard tends to get confused; sooner or later it either flickers or gets stuck.
I tried the "Web Browser" controller template, but that doesn't help.
It might be possible to improve the screen layout and lock the keyboard in place. However, you'd then be playing on the top half of the Steam Deck's landscape-oriented screen. It's just not a lot of space for text.
(Bluetooth keyboard? I couldn't get mine to pair. If you succeed, let me know if it works.)
The upshot is that parser-based IF support is not a priority for Steam Deck right now. Apologies! I'll let you know if that changes.