I did it! It took me 152 or so in-game days, but I discovered one of the Elder's altars rather close to my base and the world spawn.
https://steamcommunity.com/sharedfiles/filedetails/?id=2750265272

The altar is where I am on the map:
https://steamcommunity.com/sharedfiles/filedetails/?id=2750266005

Next up, Bonemass... but I don't need him for the wishbone. Just the power, eventually.