Hey, thanks for the reply. Do you mean in system > cycles render device ? Anyways it says of course "no device for path tracing, cycles will render on CPU" because I'm on Mac. As I mentioned when navigating in the viewport, I can see that the Vega is running full on in the activity monitor so it is detected and it works but it seems odd that 32 Gb of ram + a Vega Frontier can't handle a single oak tree with his leaves smoothly when switching to lookdev or rendered. I already set the viewport sampling to 16 but is there any other settings that could be tweaked? Maybe in memory and limits...? I'm pretty sure it's a dumb simple thing but I can't find the solution and it's kind of frustrating considering the investment...
Also these blender crashes and slow viewport render frame rate with RadeonProRender (compared to cycles) are still a mystery! Even when everything is up-to-date.
The thing that work incredibly good is the rendering with RPR and the Vega. Very fast and pretty. Love it