I know it's a small group but if anyone wonders you can play the game on Steam Deck now.
The game uses Microsoft Edge WebView2 which couldn't be installed on SteamOS before but can be now. You don't have to install it yourself before launch, the game will do it for you on the first launch.
Afterwards the game will give you a black screen for some time, maybe a minute until you can pick your language so just be patient. For some reason the game launches in Windowed mode and the main menu doesn't have a Settings option at this point, you have to start a new game to get the Settings option and to change to Fullscreen (which you want with Steam Deck because the text is rather small in Windowed Mode).
You have to change the controller layout but after that you are good to go. (If the developer reads this, automatic controller settings on Steam Deck or if a controller is used would be great but I understand that it is an afterthought at best for most. Right now I'm just glad it runs on Steam Deck at all because I prefer it over using my pc for games like these)