I'm using FlightGear 2018.3.2 on Windows 10 1809 with AMD drivers 19.4.1 (that is no April fool's joke).
OGL based Furmark pushes the Vega card up to roughly 1600 MHz and ~100 fps, so I gather the OGL driver generally works.
But
with FG I see at max. (!) only 900 MHz, while *typically* the Vega card is driven to even run only at ~300 MHz by FG.
At the same time I see CPU usage at 4-5%, which is the equivalent of 1 thread of the CPU.
That results in
~20 fps with ALS and ~10 fps with Rembrandt.
As a side note, I get a pixel trashy screen during startup of FG when using the standard renderer (with or without ALS),
while with Rembrandt the splash screen looks OK.
After startup/loading, when the simulation is presented on screen, the picture looks good no matter which renderer I use.
And
when I use the "reset" menu function the splash screen looks OK during re-initialisation with any renderer.
What am I missing ?