Thank you for your response. I checked the folder and it is unfortunately empty.
This thread reports an error similar to the one related to the GVA encoder. The error popped up with another software apparently because of a conflict between OpenGL and QtWebEngine. I found some evidence that RStudio uses QtWebEngine to render things onscreen (thread here). Someone also had the same issue on Ubuntu with different hardware (thread here). I have not found a way of changing the rendering engine on RStudio though.