Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
When I see the ability to simulate mountain wave properly in a sim - is the day that I know these computer wizz kids have really cracked it.
For example, I know the situation of P3D very well: default thermals are dumb with no ridge lift. Addons like CumulusX or ActiveSky bring better ridge lift.
What is the situation in XP11 ?
FlightGear has lee waves since 2010. https://forum.flightgear.org/viewtopic.php?f=5&t=9566
Very basic thermals; nowhere near Cumulus X.