I get a lot of ads everywhere. And trackers. On most of the news sites, social media platforms, my email provider, .places where I look up information, … The majority of the internet is commercial and financed through advertisements. With few exceptions, like personal/indie blogs and places like this one. I mean if you read just blogs and Wikipedia, you might already be alright. But that’s not how 99% of people use the internet.
Yeah, Youtube ads won’t be blocked by a DNS blocker. You need a browser plugin for that. I use Firefox, uBlock and Sponsorblock. That removes most of the ads everywhere, including Youtube.
I’m not sure about anything useful. Best thing would probably be to install Linux and donate them to people in need. For experimentation, sure, set up a Beowulf Cluster, learn FreeBSD, Orchestration, Kubernetes, Ansible… Use them to test your microservice architecture software projects, software-defined networking…