Any! My guess is OSM's official tile server is probably the most reliable, but I really have no idea. Since maps are currently broken on Miraheze, I'm guessing not too many wikis are actively using it. Thus, I suspect we wouldn't meet the "heavy use" that is forbidden in OSM's usage policy.
I do not know how production Kartographer works. I'm guessing you all are using Kartotherian, and the tile server is configured somewhere in there.
Hi @Reception123. Any updates on this? I realize this is super low priority, as I'm probably the only one actively looking for maps (or else presumably you would have received other such requests). This is why I would like to help, but I'm not sure where to start. I was unable to find any documentation on setting up a "kart", could you point me to that? Also, where is the existing Kartographer/Kartotherian configuration for Miraheze? Many thanks for the help.