I created the following dashboard to have an overview of what was going through the squid proxies:
One of the talk talkers are Prometheus hosts. For example prometheus1006 2620:0:861:102:10:64:16:62:
Using HTTP CONNECT (so HTTPS) towards (top 5 hits for 1h):
[2620:0:861:ed1a::1] - 1,137 184.108.40.206 - 120 <-expected, external host (automatiic) en.wikipedia.org - 120 donate.wikimedia.org - 119 220.127.116.11 - 60
Not sure what those are for, but they probably shouldn't use the proxies to reach internal services (unless it's to monitor the proxies themselves).
However feel free to close the task if it's working as expected.