Loss of coolant summary, please.

[abscate]

We can borescope them up here and look for whistle clean cylinders and pistons, but I’m betting a thin split hose somewhere

[Roger_850T]

The trouble is that often when things leak hot, it evaporates immediately and can't be readily seen. My preferred way to look for coolant leaks is to pressurize cold. I have a "tee" fitting that I put in the line going to the top of the overflow tank, and I have a gauge and a Schrader valve. I'll pressurize it to ~15psi and wait. (Cap should vent at 1.5 bar, or 22.5psi.) It should hold pressure overnight, easily. (Dropping a few psi is ok, but should not get to zero.) When cold, you should be able to see the coolant leaking out, sooner or later. Pull the spark plugs, look down each bore. Leave it overnight - eventually drips will probably make it to the ground. Feel for wet carpet. Pull back the covers (carpet plus black plastic cover) and look at the bottom of the heater core. Check the edges of the radiator where the plastic end meets the core. Check where all the coolant hoses connect. With luck, you'll find it in 30 minutes, but maybe it will take overnight.

Good luck!

Roger