When I first installed Cura 4.9.1 It crashed on startup. Turns out I need the dll - opengl32..dll. I downloaded it from here:
Once downloaded, unzip and place the opengl32.dll file in the main Cura program folder (not any of the sub-folders}. On my installation the path is C:\Program Files]Ultimaker Cura 4.9.1.
After that Cura has worked fine for me.