What is a residential proxy network?

  $ whois 52.202.152.73
  OrgName:        Amazon Technologies Inc.

I guess Amazon? Would be funny if this actually ran over Amazon Sidewalk but I doubt that.

You are looking at the IP of lumtest.com not the service behind it which is what the OP was referring to.

A wretched hive of scum and villainy.

But seriously, it's basically a front end to a bunch of people who have been incentivized (or fooled) into installing a proxy server on their home computers. It's primarily of interest as a way to make certain types of fraud (like ad fraud and credit card fraud) much harder to detect.

yeah that seems interesting

One note is that that one doesn't seem to support ipv6