Holy cow dude.
How many ports would you really need? The mikrotik crs310-8g-2s-in has 8x 2.5gbps ports and 2x SFP+ (10G) ports. I think I got mine for either $200 or $250 (can’t remember). It doesn’t use a ton of power (it has a 24v 1.5A = 36W brick), but it does have a fan. Mine hasn’t seen much usage, but the fan is fairly audible even at idle. I’m still happy with it (TBCH it’s sitting near me around my ear level maybe a foot away or so, so that’s probably why I find it loud).
I’m not familiar with the 2nd hand market, you might be able to find a 10G copper switch with more ports for cheaper. But you need to consider the power consumption of it (which is likely to be in the 50W+ range) and if it supports multi-gig (AFAIK most older switches only support either 1 or 10G and not multi-gig). If you get a SFP+ only switch, it’s all on the transceiver to support NBase-T.
Now as a better question: do you need multigig? I might sound pedantic, but gigabit is still plenty fast for most things in the home. Sure, it’s nice to have more speed, but unless you’re doing video editing directly on your NAS or you’re running a bunch of VMs from network storage, then gigabit is still ok (and you can get away with gigabit too for that scenario if you configure it well). If you’re streaming 1080p on your network, you need about 6-8 Mbps. For 4K you need between 25-200 Mbps for the highest quality, bitrate and hdr (so still gigabit).
To go over gigabit over the internet router, you’d have to be streaming 5x 4K streams at once and you wouldn’t be watching 5 movies on 1 device, but on multiple devices, which means the individual devices still wouldn’t need that much oomph. But the bigger backbone is nice to have just in case.
Now, for your local network, all that >1Gbps connection will give you is less waiting time when transferring large files. I can’t think of a single thing that would require that bandwidth / throughput on 1 device (aside from multiple VMs running on a single NAS from a different hypervisor box).
I think there’s a couple pi-hole tutorials on the forum. I prefer blocky because it’s deployable in minutes, it’s minimal and the config isn’t too complicated for getting started (although it’s all CLI, so you might want to avoid that maybe). Pi-Hole still requires some CLI’ing, but once you’re in the webgui, you’re off to the races. That can run on any old SBC and even on a pi zero w 2 over wifi (it needs neither throughput, nor latency, it’s just a local DNS server).
Of course, if you want to do more things, like DNS caching or recursive DNS, you might need just a little more oomph than the zero w 2, but nothing too crazy.
