Hi, sorry to chime in!
It's very difficult to run Itch Windows game on Steam Deck; Steam just quits and doesn't run it, and Lutris just won't find the existing files it's pointed to.
I did the same procedure I did for other Itch games and while it works well on my Linux Mint desktop, it won't on my Steam Deck.
Maybe it's the ARM CPU, maybe it's Arch Linux, but it's difficult to get them to run.
Could you maybe consider a Linux build?