Another NOT recommended method to Enter Recovery mode and flash M17/FM Firmware (Demo reference to @Alan Spot)
Step 1,
sudo mount -o remount,rw / ;
cd /home/pi-star
hex_file="mmdvm_f4_m17_build20230606.hex"
echo "hex_file:${hex_file}"
rm -f ./${hex_file}
curl -OL www.bi7jta.org...{hex_file};
curl -OL www.bi7jta.org...
sudo chmod +x stm32flashV5;
echo "Stopping Pi-Star Services..."
sudo systemctl stop pistar-watchdog.timer
sudo systemctl stop pistar-watchdog.service
sudo systemctl stop mmdvmhost.timer
sudo systemctl stop nextiondriver.service #Must stop NextionDriver
sudo systemctl stop mmdvmhost.service
sleep 1
echo "Killing any remaining MMDVMHost processes..."
sudo killall MMDVMHost
sudo killall MMDVMHost_NoOLED
sudo killall MMDVMHost_Adafruit
echo "Starting Flashing..."
Step 2,
sudo /home/pi-star/stm32flashV5 -v -w /home/pi-star/${hex_file} -R /dev/ttyAMA0;
Step 3,
See the MMDVM hat flash process status.
Good luck !