Comment by joveian

Mullvad in particular has a page that lists the ISPs they use (in a few cases their own servers at a datacenter), although they don't list the datacenters (sometimes you can get this info from the ISPs).

https://mullvad.net/en/servers

They also have a document that lists some of their practices around the servers, such as not using shared servers:

https://mullvad.net/en/help/server-list

I noticed that the website of one of the two providers they use near me was over a decade out of date :/. DAITA is Mullvad's anti-traffic analysis framework, without it a single hop can likely be easily deanonymized by logging by a single party (it isn't clear if multihop uses fixed packet sizes between their servers).