SOLVED: How can I reduce ADC jitter

[Demon]

stick a 2200uF low esr electrolytic in every power rail on each bread-board and be done with it. if it still noisy add another set....

I only have a few 1000uF electrolytics, so I put 2 on each rail, same ADC flutter of mostly 1, sometimes 2.

...if that fails isolate noisy bits behind rfc's [rf chokes]....

I only have these 2 on hand:
RL-1284 100uH, https://www.electronicsurplus.com/re...uh-irms-0-4amp
79F101K-TR-RC 100uH, https://www.mouser.com/datasheet/2/5...te-1371239.pdf

...ditch the hi switching speed [noise inducing] mosfets for pwm, use bjt instead, its only a backlight...

I was having difficulties turning the backlight all the way off using 2N2907A PNP. The BS250P P-chan worked like a charm from full OFF to full ON.

...as ioannis says, breadboards and low noise are very close to mutually exclusive concepts

Yeah, that's why I moved away from my larger main prototype board to only 2 PCB boards to get ADC working perfectly.