Yes, sadly Little Snitch (or a similar app) is required to tame Firefox. It's a real shame since they use "Privacy" as selling point, but for me that starts with being transparent about what they do behind the users' backs with very clear ways to disable any nonsense (no about:config or policy BS, but proper GUI exposed options), or even better with a proper opt-in to those "security" and comfort features.

It pretty much eroded any trust I had in this browser and Mozilla (they are no more better than Google, Meta, Apple in that regard.) If it wasn't for uBlock Origin and availability for older OSX versions I would ditch it (the Dynasty build is the only option I have for a recent browser on my old Mac.)