Happy to report that on Linux Mint 22.3 Zena, I was able to run this without trouble using Heroic. I just added it and pointed to the .exe, used the latest Proton I'd happened to fetch ("Proton - GE-Proton-10-29") and hit Play.
I missed the very first screen defining Duppy though, it went by in less than a second. Also it wasn't at first clear if there's a way to pause/save/etc. (escape key or hovering over the top bar like many other games didn't work; I eventually figured it out when Tashia had a lightbulb!)
Lovely art/anim style, music, humour, and gameplay! Can't wait for the rest! =)