The Pi is familiar and comfortable for a lot of people who wouldn't otherwise use Linux or run any kind of server. It's genuinely not the best option in a lot of respects, but it's also the only thing a lot of people know and going to a dedicated server or generic Linux/BSD router seems intimidating, even if they appreciate the possible advantages.

Pi Hole was started specifically as a project targeting the Pi. It wasn't the first to do ad blocking DNS by a long shot, but it did marry a nice web UI to DNS and made it a lot more accessible. Nowadays I think there are much better options like AdGuard that do the same thing, but "running PiHole on a Pi" is a tangible thing to do with the RasPi you got as a gift and is an approachable project for a lot of Linux beginners with real benefits. You can find a million people on YouTube recommending exactly that, and walking you through how to do it step-by-step on a RasPi. Lot of people who are interested in tech but not so skilled probably don't have dedicated servers or know how to set one up, and I expect PiHole on a RasPi gets a lot of momentum from that as something cool and actually useful to do that isn't actually difficult/there are a million tutorials for.

Tl;dr is I agree with you, there are clearly technically superior options. But for a lot of the people you're referring to the alternative is not to run something better on a dedicated server/router, it's to do nothing at all and go back to using the router from your ISP.

I'm one of those users -- I set up a pihole as my DHCP server to get ad blocking on all devices on my network a few years ago and haven't really thought about it since. Raspberry Pi was familiar enough. Networking in general is mostly Greek to me, so it wasn't the easiest thing to do, but it's pretty much been set-and-forget since the initial setup (aside from updating pihole itself and the web interface every few months).

I've seen AdGuard recommended a lot recently but from what I can tell this doesn't do the same thing as a DHCP pihole.

Something I'd love to do some day is replace my consumer router with something open source and run an all-in-one solution (ad blocking for all devices on network, DoH, as well as just a generally competent home router for a small apartment). Do you have any recommendations for where to start if I were to go down this road?

Easiest first step is to see if your current router has support for OpenWRT. I find OpenWRT kinda hard to use, but a lot of people swear by it and it's very capable even.

More powerful options are projects like PfSense or Opnsense, but those require more expensive hardware and for most uses you probably also need a separate switch. I personally use PfSense and find it relatively easy to use while being extremely powerful, absolutely jam packed with features but an accessible WebUI and clear documentation.

Probably the best all round option are the semi open, prosumer-ish products from companies like Ubiquiti or gl.inet (the latter is even based on OpenWRT, but with a nicer UI... I have one of their routers as a travel router). Ubiquiti's Unifi routers are very easy to use and jam packed with features for a pretty great price, but their platform is not truly open source. Still, gl.inet or Unifi are what I would probably most recommend to someone like you looking to upgrade but feeling overwhelmed by lack of knowledge.

Beware it's fun to tinker and that's how I learnd pretty much everything I know about networking, but breaking the Internet will not endear your new toys to your family. It's good to have a spare in case you mess up so you can keep the bits flowing while you undo your mistake. Anything you choose is going to be an ongoing learning experience if you're starting from no knowledge, but there are lots of high quality tutorials on places like YouTube.

Thanks a bunch. I have actually used unifi routers in the past and didn't always have a great experience with them, but it's been a while and I feel like I might be ready to try again. Will also look into gl.inet, thanks!

Unifi has improved a lot in very recent times in terms of both features and ease of use. I wasn't that keen on their router/firewalls previously, but I quite like them now and the prices on some of their gateway hardware are unbeatable. The Unifi Express is $150 and includes a built in access point and runs their software stack so you don't need to host it elsewhere like you used to. Only real downside is it doesn't have a built-in switch, but a cheap dumb switch should be plenty for normal uses and you always have the option to buy a Unifi (or other brand) managed switch if you want to do more advanced stuff.

Some of Ubiquiti's old EdgeRouter line supports OpenWRT. I'm running it on a Ubiquiti EdgeRouter X. I doubt any of their newer Unifi stuff does though.

In classic HN fashion I forgot to mention that the nice web UI must play a key role here, and make up for all the other UX issues that come with using a pi rather than just “apt-get dnsmasq”