With a VPS it gets a bit more complicated, I probably wouldn't try to do pi-hole on a VPS though I think it would technically be possible. Regardless, I think your major blocker will be that you mentioned your router doesn't let you change the DNS server. pi-hole is a DNS server from the point of view of your router. You need to be able to change the DNS server for it to work. And if you can change your DNS server, then Adguard free plan might be an easier and cheaper (but less fun) way to get that.

I thought you might be able to pick up a really old Pi for cheap, I have pi-hole running on an original Raspberry Pi model B, but there aren't that many and even the ones that are there are more than I thought they would be (e.g. I can see a Pi 2 for $40).

People often use old laptops as a server, if you have one of those lying around.

[–] liv 2 points 1 year ago

Yes and no, I'm still using my 2014 laptop as, well, my laptop!

All this is super interesting. I'm filing it away in the back of my mind.