I’ve had a pi 3 something or other running this for a while now, works nicely.
Doesn’t have to run on a pi just any Linux based system really, could probably run it on a NAS either natively or under docker for example I’d imagine, or just on a VM.
Have mine running DHCP as the stupid BT smart hub thing doesn’t let you change what DNS servers are dishes out, so disabled DHCP there and have the pi doing it (may change the router at some point but for ISP provided kit it’s actually not bad on the whole).
Works well, wife hated it as it blocked some things from working and it doesn’t exactly give you an indication without logging into the thing, so set her devices manually to use a different set of DNS servers, but does the job nicely for everything else.