I’ve still got 8 speed on one of my bikes, it’s not that hard to source parts for 7/8spd really, just hard to get parts from the blingier groupsets, any mech current will work what ever the number of cogs…
I have to say while I find 7 and 8 speed more than adequate, I don’t think they are actually any “better” than 9spd, current mid level 9speed (Deore, tiagra SLX) stuff seems to shift very smoothly due to the slightly smaller sprocket pitch, one mans “crisp shift” is another mans “clunk”, it’s all marginal, and makes no difference to my enjoyment, I will be ditching my one remaining 8 speed cassette and shifter in the summer I think, once it’s time for a new cassette and chain I may as well chuck in the extra £20-ish for a new deore 9spd shifter…
I’ve never owned Cable discs, obviously my road bike has cable calliper brakes, and my next SS build will deliberately have V’s…