A Raspberry Pi is great if you have a need for which it excels. GPIO, extremely low power requirements, tight space constraints. But the Pi should not be the first thing you reach for when “Unobtrusive and Inexpensive Linux Host” are the only requirements.
Years ago I migrated my Pi-hole from an actual RPi to a NUC-sized system based on the AMD GX-415GA that I paid $5 for bare bones, roughly $45 all-in with PSU, 4GB RAM, and SATA SSD. It’s not screaming fast but it’s still overkill for something like Pi-hole. More importantly, it boots faster than a Pi and the storage is WAY more reliable than micro-SD cards and those things are kind of a big deal when DNS being down effectively means the Internet is down. At about 7w in use the difference in power consumption is about a penny per day.
More recently I wanted to build a stack of Docker servers to run a couple Frigate instances and consolidate my sprawl of containers running within VMs. I bought this stack of HP Prodesk 600 G4 micro desktops for an average of $260/ea. Two came as i5-8500T / 16GB RAM, one i5-8600T / 8GB RAM, all with 256GB NVMe drives. That’s a lot of compute in a tiny package and I’ll be upgrading them all to 32GB / 1TB NVMe.
A complete Raspberry Pi 4 Model B 8GB kit is admittedly cheaper — typically $150 these days — but you can find complete i5-6500T systems in that ballpark with 8GB RAM and a hard drive or small SSD. Lower specs, or i3-6100T systems, can get down to $100. Again, for the money a 6th-gen Intel CPU is a ton more compute than a Pi, provides faster and more reliable storage, and you don’t have to put up with the quirks of Raspian or running an alternative distro that has zero community.
Granted, these are systems that will idle at 10-15w and can hit 55-60w at 100% load. There are situations where that may be unacceptable but that’s probably not the situation when you’re building a tiny Linux server at home.
Once you start down the rabbit holes of Pi-hole and Home Assistant, you’ll probably acquire a bunch of other things to run — I’m at 10 distinct Docker-ized stacks and have a few more things to migrate — and you’ll be happier having starting with one system that’s overkill for everything you’ll want to throw at it than accumulating a bunch of limited-purpose RPis that you’ll eventually want to consolidate on something more powerful anyways.
If you’d like to learn more about tiny PC options, check out ServeTheHome’s TinyMiniMicro series. I specifically looked for HP G4 systems from the MP9 / ProDesk 600 / EliteDesk 800 lines because they have dual M.2 M key sockets plus an A+E key, which provides maximum flexibility for NVMe storage and Coral TPUs.