I thought that could only happen in third world countries like the US but unfortunately this is in France. I'll reboot my phone to show you.

Edit : well, apparently that's related to connecting to the carrier's network because right now I'm in another country and it doesn't happen

I can show you a screenshot of the shitty app it installed the first time that happened, that it appears I can't uninstall without rooting the phone. Keep in mind I bought the phone directly from Fairphone so it was not "SIM locked" to my carrier :

I looked again for more info about that app and it appears they are pulling that shit with the phone constructor's consent. After all they are the main mobile phone carrier in France by a huge margin, which probably helps for these kinds of deals. I would have liked to have been consulted too though...