That suggests also that QEmu isn’t the right software when fiddling with raw x86 assembly to write an OS (qemu is the recommendation of oswiki though).

So what is? One would need software supporting debugging. VirtualBox supports that I think, but I don’t know if that works if it runs on top of Hyper-V - which is enabled by default in Windows due to some security features (and I don’t want to disable that anyway).