How to change the charging chime on MBP (PowerChime.app)
I had the same exact question, Googled it, landed on here and found the answer hours later, lol.
If you're still looking for the answer, or for anyone's future reference -- after disabling SIP and restarting, open terminal and run:
sudo mount -uw /
killall Finder

... and you're good to go. Just proceed to replace the .aif file in &quot;Powerchime.app&quot;. For me, I changed mine to the old iOS charging chime!
Haha