“no other restrictions have been announced regarding hardware” means it’s OK.
I have been using hardware with 20 PCs (Personal Computers) all connected to one keyboard/mouse with a USB KVM Synchronous Switch. I have been doing this since about the middle of November 2020 and also live stream. I go to where the most players I know are, Orgrimmar and Eastern Plaguelands. I also live stream while doing it. Since the middle of November I have not received any warning or suspension. The point being, it’s ALLOWED. The NeverBoxers don’t want to hear that but check out the PreparedWoW live stream if you would like to see 20 boxing with hardware legitimately.