Yes, I'll tell my mother to host a PiHole.

Of course bringing it with her would require something to tether it to other than the phone she's actually using as a phone (I think), and a way to power it all. She's going to need a bigger purse.

Or she could access it remotely. I doubt her residential DSL comes with a static IP, so she's going to have to get a domain name and set up dynamic DNS... oh, and route the appropriate port to her Pi through the ISP's NAT router, assuming it actually supports that. Maybe she should buy the latest fancy one from GL.iNet with those big antennas and OpenWRT.

I think I might send her that AdGuard link instead.

Neither this screenshot nor their website claims to block ordinary advertisements.