The minimum video memory requirement can be changed in:
C:\Users\me\AppData\Local\ov\pkg\marbles_rtx-2021.1.5_build\windows-x86_64\release\apps\omni.app.marbles.kit
you should find renderer.minGpuMemoryMB = 11000 on line 37
Lowering the minimum should allow the application to run on something like a RTX 3080 or 3070, but I can’t guarantee that you would get at least reasonable performance, nor can I test it for you because I only have a RTX 3090.
Hope this helps!