System: Dell XPS13 9370 + Razer Core X Thunderbolt eGPU + Radeon HD7970. Windows 10 build 1909 x64 Firefox 75.0 x64 No profile changes made to enable webrender, so this is disabled. I am using the standard Windows control for ejecting my eGPU when I am finished with it. By default Firefox was using my eGPU, meaning that when I attempted to eject it, I was told that five Firefox processes were using the eGPU and preventing a clean eject. In this configuration the AMD card showed up in about:support as GPU#1 and Intel as GPU#2, WebGL render was shown as AMD I used the standard Windows Graphics Settings to force Firefox to use the "Power Saving" GPU. This moved the Intel card to GPU#1 with the AMD as GPU#2. WebGL render is now shown as Intel. Unfortunately, when I go to eject my eGPU, Windows complains that one Firefox process is still using the eGPU and won't let me do a clean eject without first closing Firefox. My question is, why is Firefox apparently still using GPU#2, and is there any way to stop it doing this?