Great. So I might assume this is from a working desktop?
It shows PRIME functioning as expected.
Now … of course … most people prefer to have their iGPU be used most of the time, and then only use the dGPU for intensive tasks like 3D gaming.
(ex, steam game options with prime-run %command%)
But if you really want to be able to boot into just the iGPU or just the dGPU for whatever reason, and the more manual methods are not acceptable, ie: you want a switcher utility thing…
Then I would suggest envycontrol as one of the more reasonable options.
So far it looks your problem was just optimus-manager itself.