I run 4 witness nodes in 4 separate locations/countries.
2 are hosted in 2 different Cloud Service Provider's datacenter, mainly because they provide reliability and high availability for power and connectivity, with SLA. This is a key factor when you are a top 20 witness.
The 2 others are hosted in different secured professional IT rooms, which I have physical access to, one of them being under my sole control and ownership.
Jeez, I just posted my "report". Let's see. I'll edit to get you in. 😊