To make this detection really reliable I had to change the RTC register check like this:

Wire.begin(21, 22);
uint8_t reason = M5.RTC.readReg(0x01);
// now it's safe
M5.begin();
// check reboot reason flag: TIE (timer int enable) && TF (timer flag active)
if ((reason & 0b0000101) == 0b0000101) {
    restartByRTC = true;
    Serial.println("Reboot by RTC");
} else {
    restartByRTC = false;
    Serial.println("Reboot by power button / USB");
}

https://github.com/dheijl/M5Core2MpdCli

My RPI MoodeAudio players do not have a display, so I added a remote one, using the M5Core2, that allows me to:

• load the initial/updated config from SD and save it to flash (NVS)
• select the MPD player from a list if you have more than one player (I do)
• see what's currently playing
• select a favourite radio station from a list of favourites (configured in Moode or not, the url is all that MPD needs)
• stop/start playing

I suppose it would work with any MPD based audio player.