You can run just run whole Windows with IE6 in the browser these days thanks to WebAssembly:
https://oldweb.today/?browser=ie6. It even works on my phone.
I’m not very optimistic given how tightly this thing is coupled to Windows and ActiveX, but I might still give it a try just out of curiosity.
Only problem I see is, does it need custom hardware/drivers? If yes and you can make hardware passthrough work with qemu, perhaps you could host a VM instance on a server and ship some web UI or RDP client for users to connect to it.