In those cases, would using a 6 bit + FRC monitor be much more straining than using a true 8 bit monitor?
I personally find a monitor to be either straining or not. After a period of time either a monitor will cause me pain or it won't, I presume it is either ok enough that my eyes/brain adapt or they don't, and I experience pain. I find I can adapt to most monitors that use 6bit + FRC, but I rarely find graphics cards with use FRC to be acceptable. Why does monitor FRC affect me less than graphics cards? I presume monitors have a dedicated FRC chip, that does a good job at it, whilst GPU chips are not really designed to be good at FRC.
Does the true 8 bit monitor still dither?
Its difficult to know, whilst an 8bit monitor does not need to dither to produce 8bit, it could still be designed to dither to produce better colours etc.
Re linux, no idea, but there are people here that use it.