It's a .NET application that still potentially relies on some third-party x86 binary drivers/components that are only on Windows. Ideally in the future the whole codebase could be ported over to .NET Core, with the remaining native components being stripped out (we've somewhat worked towards this).

Really though, it's that we don't have the resources to dedicate to any porting or compatibility effort (I've toyed with the idea of QEMU on ARM) to do it, so unfortunately it's one of those things that gets very slowly pieced together in the background here and there. Too big a project to convince the higher-ups that it's worth the tradeoff of prioritizing it over new features and new customers.