With $$$$ in mind I'd set the yurt atop a wood framed platform since a full fledged foundation really should have a stick frame house atop it. jmo. Enclose the water supply and drain in an insulated chase below the platform. Insulate the chase with foam board instead of fiberglass batts. Wrap heat tape around the supply as a backup for extremes in low temperature.
Below grade down to frost line you need an open pit so no earth is in contact with the pipe. Wrap the pipe with heat tape and pipe
. Insulate the snot out of it.
Standard procedure for house trailers in extreme cold climate like northern Wyo. is described above PLUS the addition of insulated skirting around the base of the trailer. What I have described to translate to a yurt, but alll that pipe in the yurt HAS to stay above freezing
Really imo yurts are NOT good candidates for extremely cold temperatures when it comes to modern plumbing because the arey gonna be prone to freezing unless a conventional furnace is utilized. And/or drained when away.
IMO if you are remotely considering a foundation, I'd consider building a small ranch house on top of it. But this is jmo.