Oh what a surprise!!! Another surprise. You forgot to explain that Android (and MS) started behaving this way after Apple made clear how to make money, leveraging the ignorance of the herd. I hope you publish soon a cleaned up ROM for the iPhone as well. Oh, wait...
Green is such an ugly color on you... in the real world I would have already beat the living daylights out of you for being such a douche...
Another good option for your mum would be for you to to install a VPN app on her device like Wireguard, and setup a VPN host on some cloud provider like Digital ocean, Hetzner or host it yourself why not. This way you can also control the device via DNS and IP filtering. I would personally install Lineage and forget about having to deal with compliling your own Android fork. If you, or your parents, have good enough and compatible router, you can host the VPN server and do filtering on it with OpenWRT.
um, I have been building android before cyanogenmod and lineage were a thing... and they severely alter the aosp code to the point that most of their apps and services and framework are not buildable in aosp and they support signature spoofing and gms compatibility so no, they are a terrible option and should never be used. I will stick to doing what I know works. VPN is built in to Android at this point, however using Google relays...
So a current stock ROM is made by Google using for 50% or so closed source and proprietary, apple like, crap, and your problem are the "alteration" made by Cyanogen? Of course you want the signature spoofing, avoiding the google services is one of the main point of using a custom rom. Which is your point in building a custom ROM? Peacoking?
Insults from brainwashed Apple fanboys are always taken as medals of honor by sane minded people. So thanks.