Glad to hear you're enjoying the game, and that you have friends who are too!
I don't have any explicit rules for playing Dungeon Hero multiplayer, but I imagine you could have a shared pool of stamina and resolve, and then each player makes their own traits. Or perhaps distribute the available stamina and resolve across different players. For each situation, you simply choose two characters' traits to bring to bear. Should be balanced largely the same as the single-player version except you'd have more opportunities to use d12's and d10's, so you might also make a rule that you can't have more than one d12/d10 in a roll or something. If you try this, I'd be interested to hear how it plays out.
You might also be interested in Fable on Your Table, which is a game that uses similar mechanics but with a tabletop miniatures setup. It's also solo-only, but I'm currently working on a version that can accommodate multiple players.
There's also Welcome Aboard, Captain, which is also based on the same system, but in a more Star Trek / Babylon 5 / Orville type setting. That has rules for generating challenging procedural missions that are very similar in structure to the Dungeon Hero games, and it includes rules for playing it multiplayer, with players taking on the role of different bridge officers. There's a free preview adventure called Charon Wormhole that introduces the game, its mechanics, character creation, and the setting; you can check that out to get a feel for how that game plays out.