I disabled any data collection using the GUI some days ago:

However Firefox still regularly tries to connect to this address incoming.telemetry.mozilla.org, which is apparently blocked by my network.

Now my question - why does FF try to connect, what is it and how do I stop it?


I was aiming at the “How do I stop it” question. - Either use librewolf, or compile a custom version of firefox applying whatever librewolf does to disable that.
But are you not already stopping it with your firewall?
It is true I am stopping it. But I would like to understand the reasons why FF is making this connection despite disabled telemetry.