1- move your music to a pc
2- install foobar2000 (next,next,,,,finish)
3- drag and drop all music on to foobar2000 gui
4- select all (ctrl+A), rightclick, replay gain, per-track gain. after it finishes job (needed time depends on your file types and amount) all your music is tagged already.
5- move replaygain tag added music to your phone again.
6- don't forget to open ReplayGain settings in Poweramp, as in 2nd video
7- enjoy
foobar2000_replaygain.mp4
screen-20230704-1535122.mp4