Guess the easy fix is out the window then. Reading about all these hifiman issues have kept me from buying even the 400se(which is constantly on sale for pretty cheap in my country).

Is it the cable or the connector bit on the headphone that's the issue? You can try diagnosing by swapping the left and right channel ends of the cable and see if that fixes the problem on the right side. If it is the cable then getting a replacement aftermarket cable for cheap shouldn't be hard depending on where you live.

JCALLY TC30 PRO fits the bill. Has all 3 earphone connector types on aliexpress(can't post links here)

Wavelet on android devices does have channel volumes. As do many(most?) android phones with android 12 and up in accessibility settings. For PC equalizerAPO works, as mentioned already in this thread