I use it on a Raspberry Pi 2B and Orange Pi Zero, both work wonderfully for the task, and it looks like Pi-Hole can work fine even on a router. Both of my SBCs are passively cooled, that’s why I decided to comment on the photo: you don’t need a computer this powerful to run it. As far as I remember, my very first Raspberry Pi (v. 1B or something like that) handled this task very well too. I temporarily retired that SBC in favour of Orange Pi Zero, so I cannot say for sure, but I think that computer had no issues with being fast enough for Pi-Hole. Really, give it a try if you didn’t, it’s ‘install once and forget’ type of software. Perhaps it should be updated periodically, but I don’t manage that. The only nuance with it, you need to have two computers, for the redundancy. Otherwise you’d be having downtimes when you need to turn off the SBC, or even reboot it.
What do you mean by the easiest way? For me, that’s pretty simple: backups. In general, it’s a nice idea to have your /home separated (partition or disk), but in reality, I don’t bother. I just do backups. Considering things are mostly in the cloud (e.g. browser bookmarks), the backups are usually just the files, rarely some configs. That’s why I don’t bother separating home even for myself. Most times reinstalling something is not an issue. Actually, rather teaching someone using the interface is more of a problem.
That’s why I wanted to ask why did you choose Mint for your task? I’m trying to migrate one place to Linux off Windows, all they do is basically browser and some printing (I checked, their printer works out of the box with Linux). I settled with Fedora atomic desktop. First I wanted Kinoite, as KDE is very similar to Windows, visually. But I gave it some thought and realised it’s too complicated for a basic use case, and Gnome is just very good and simple, and perhaps it would be just not too difficult to have them learned the new interface. It’s not much after all: the top left corner, plus top right corner to power off the machine. I expect them to get familiar in no time, but I’ll see how it goes over time, as I have just installed the whole thing very recently and haven’t migrated them fully yet. (I have to transfer their files to the new SSD I bought them, before giving them the new system.)
I thought of Mint myself, but I don’t like Ubuntu, never liked Mint, and I thought I’d prefer something more modern. I just have very positive, mostly positive, experience with having Fedora at home, it was mostly great for years, with some occasional inconveniences. But since I’m pretty experienced with Linux, most things could be fixed within minutes. I’m yet to discover how it would work in the wild.