Arduino in the same vein. There's a great "30 Days Lost in Space" tutorial set, but even to play around with by yourself for cheap, you can get an off brand (the hardware is open source!) Arduino Mega for 20 bucks. All sorts of cool programming and electronics fun.
AdGuard Home is better since it supports DNS over HTTPS, which prevents your internet provider from seeing and intercepting your DNS queries (which they can do even if you use a third-party DNS service like Google or Cloudflare). You can get DoH working on PiHole but it's a lot of manual work.
It's even easier with AdGuard Home though, since it uses DoH via Quad9 out-of-the-box. People usually use solutions like PiHole and AdGuard Home because they don't want to mess with it at the command-line, just via the web UI.