Telemetry can be turned off without modifying the code. I don’t know about the legality of it, maybe in the case of Firefox the other things they do are also at most build options rather than code changes. But generally distros are allowed to make changes to the packages they distribute, that is how free software works.
Mozilla owns the Firefox trademark so if they get to choose how the trademark is used. I remember that a while back Mozilla threatened. I can’t remember if it was Debian or Linux Mint who received the threat.
Telemetry can be turned off without modifying the code. I don’t know about the legality of it, maybe in the case of Firefox the other things they do are also at most build options rather than code changes. But generally distros are allowed to make changes to the packages they distribute, that is how free software works.
Mozilla owns the Firefox trademark so if they get to choose how the trademark is used. I remember that a while back Mozilla threatened. I can’t remember if it was Debian or Linux Mint who received the threat.