Let's start with the juiciest request sent to https://o.isx.unity3d.com - the first one that included my geo, while I disabled Location Services on iPhone for all apps! If you are as naive as I was before this, you might be surprised - what does Unity, the 3D engine, have to do with the in-app advertisement or location tracking? Perhaps that's just some monitoring data to help improve the engine?
Turns out that Unity's main revenue stream (they made $2 bln+ in 2023) is Unity Ads - "Mobile Game Ad Network". Sounds quite interesting.