All of a sudden it started working for me as well. Computers… where the definition of insanity does not apply.
Looks like the lowest value that /sys/class/powercap/intel-rapl:0/constraint_0_power_limit_uw will accept without going down to 0 is 125000. Noticeable but tiny input lag at that low of a PL, but it does result in a functional system. Honestly its not much worse than my 6Y30 processor tablet pc had when it was allowed to go full speed lol. Looks like 11-12 hours of battery endurance available even with wifi on, browser open, but min brightness.
Using this and the rest of my super long endurance tweaks I detailed in my other thread, I set a new current_now record low as well, 102000!
Does not look like PL1 is hard clamped at that low of a value, though. Playing a video in mpv seems to be using more power than that according to powertop and current_now. But still a low enough draw for 9+/- hours video playback from a samba source. Not too bad.