radio stream receiver for raspi, bodged together from url mentioned in comments and a few other sources: A website with streaming urls (https://hendrikjansen.nl/henk/streaming.html) and a few adafruit / sparkfun tutorials on audio-to-usb-soundcard and readonly OS. (strangely, after routing audio to card 1 which is the usb card and setting the FS…

runradio.py

#!/usr/bin/env python3
# requires `mplayer` to be installed
# v1.0

# https://raspberrytips.nl/internet-radio-luisteren-raspberry-pi/
#modified to use vlc and a simple hd44780lcd + 3 buttons

import time
import os
import sys
import signal
import RPi.GPIO as GPIO
from gpiozero import Button

PY3 = sys.version_info[0] >= 3
if not PY3:
    print("Radio only works with python3")
    sys.exit(1)

from threading import Barrier
import subprocess
from subprocess import call


UPDATE_INTERVAL = 1

#https://hendrikjansen.nl/henk/streaming.html#po
STATIONS = [

     {'name': "NPO Radio 1",
     'source': 'https://icecast.omroep.nl/radio1-bb-aac',
     'info': "NPO Radio 1"},

     {'name': "NPO Radio 5",
     'source': 'http://icecast.omroep.nl/radio5-bb-mp3',
     'info': "NPO Radio 5"},
 
    {'name': "NPO Radio 4",
     'source': 'http://icecast.omroep.nl/radio4-bb-mp3',
     'info': "NPO Radio 4"},
 
    {'name': "NPO Radio 2",
     'source': 'http://icecast.omroep.nl/radio2-bb-mp3',
     'info': "NPO Radio 2"},
    
    {'name': "Arrow cl. Rock",
     'source': 'https://stream.player.arrow.nl/arrow',
     'info': "Arrow cl. Rock"},

    {'name': "Classic FM",
     'source': 'http://playerservices.streamtheworld.com/api/livestream-redirect/CLASSICFM.mp3',
     'info': "Classic FM"},
     
     {'name': "Omroep West",
     'source': 'http://icecast.stream.bbvms.com/omroepwest_radio',
     'info': "Omroep West"},
]

# Zuordnung der GPIO Pins (ggf. anpassen)
#switches on 26,19,13,6
nextstation = Button(26)
prevstation = Button(19)
playpause = Button (13, hold_time=3)
#onoff = button(6)

LCD_RS = 14
LCD_E  = 15
LCD_RW = 18
LCD_DATA4 = 23
LCD_DATA5 = 24
LCD_DATA6 = 25
LCD_DATA7 = 8

LCD_WIDTH = 20      # Zeichen je Zeile
LCD_LINE_1 = 0x80   # Adresse der ersten Display Zeile
LCD_LINE_2 = 0xC0   # Adresse der zweiten Display Zeile
LCD_LINE_3 = 0x94   # Adresse der 3te Display Zeile
LCD_LINE_4 = 0xD4   # Adresse der 4te Display Zeile

LCD_CHR = GPIO.HIGH
LCD_CMD = GPIO.LOW
E_PULSE = 0.0005
E_DELAY = 0.0005

def lcd_send_byte(bits, mode):
    # Pins auf LOW setzen
    GPIO.output(LCD_RS, mode)
    GPIO.output(LCD_DATA4, GPIO.LOW)
    GPIO.output(LCD_DATA5, GPIO.LOW)
    GPIO.output(LCD_DATA6, GPIO.LOW)
    GPIO.output(LCD_DATA7, GPIO.LOW)
    if bits & 0x10 == 0x10:
        GPIO.output(LCD_DATA4, GPIO.HIGH)
    if bits & 0x20 == 0x20:
        GPIO.output(LCD_DATA5, GPIO.HIGH)
    if bits & 0x40 == 0x40:
        GPIO.output(LCD_DATA6, GPIO.HIGH)
    if bits & 0x80 == 0x80:
        GPIO.output(LCD_DATA7, GPIO.HIGH)
    time.sleep(E_DELAY)    
    GPIO.output(LCD_E, GPIO.HIGH)  
    time.sleep(E_PULSE)
    GPIO.output(LCD_E, GPIO.LOW)  
    time.sleep(E_DELAY)      
    GPIO.output(LCD_DATA4, GPIO.LOW)
    GPIO.output(LCD_DATA5, GPIO.LOW)
    GPIO.output(LCD_DATA6, GPIO.LOW)
    GPIO.output(LCD_DATA7, GPIO.LOW)
    if bits&0x01==0x01:
        GPIO.output(LCD_DATA4, GPIO.HIGH)
    if bits&0x02==0x02:
        GPIO.output(LCD_DATA5, GPIO.HIGH)
    if bits&0x04==0x04:
        GPIO.output(LCD_DATA6, GPIO.HIGH)
    if bits&0x08==0x08:
        GPIO.output(LCD_DATA7, GPIO.HIGH)
    time.sleep(E_DELAY)    
    GPIO.output(LCD_E, GPIO.HIGH)  
    time.sleep(E_PULSE)
    GPIO.output(LCD_E, GPIO.LOW)  
    time.sleep(E_DELAY)  

def display_init():
    GPIO.output(LCD_RW, GPIO.LOW)
    lcd_send_byte(0x33, LCD_CMD)
    lcd_send_byte(0x32, LCD_CMD)
    lcd_send_byte(0x28, LCD_CMD)
    lcd_send_byte(0x0C, LCD_CMD)  
    lcd_send_byte(0x06, LCD_CMD)
    lcd_send_byte(0x01, LCD_CMD)  

def lcd_message(message):
    message = message.ljust(LCD_WIDTH," ")  
    for i in range(LCD_WIDTH):
        lcd_send_byte(ord(message[i]),LCD_CHR)

def lcd_message_at(message,line):
    if line == 1:
        lcd_send_byte(LCD_LINE_1, LCD_CMD)
    if line == 2:
        lcd_send_byte(LCD_LINE_2, LCD_CMD)
    if line == 3:
        lcd_send_byte(LCD_LINE_3, LCD_CMD)
    if line == 4:
        lcd_send_byte(LCD_LINE_4, LCD_CMD)
    lcd_message(message)


class Radio(object):
    def __init__(self, start_station=0):
        self.current_station_index = start_station
        self.playing_process = None
        GPIO.setmode(GPIO.BCM)
        GPIO.setwarnings(False)
        GPIO.setup(LCD_E, GPIO.OUT)
        GPIO.setup(LCD_RS, GPIO.OUT)
        GPIO.setup(LCD_RW, GPIO.OUT)
        GPIO.setup(LCD_DATA4, GPIO.OUT)
        GPIO.setup(LCD_DATA5, GPIO.OUT)
        GPIO.setup(LCD_DATA6, GPIO.OUT)
        GPIO.setup(LCD_DATA7, GPIO.OUT)
        display_init()

    @property
    def current_station(self):
        """Returns the current station dict."""
        return STATIONS[self.current_station_index]

    @property
    def playing(self):
        return self._is_playing

    @playing.setter
    def playing(self, should_play):
        if should_play:
            self.play()
        else:
            self.stop()

    @property
    def text_status(self):
        """Returns a text represenation of the playing status."""
        if self.playing:
            return "Now Playing"
        else:
            return "Stopped"

    def play(self):
        """Plays the current radio station."""
        print("Playing {}.".format(self.current_station['name']))
        if self.current_station['source'].split("?")[0][-3:] in ['m3u', 'pls']:
            play_command = "cvlc -playlist {stationsource}".format(
                stationsource=self.current_station['source'])
        else:
            play_command = "cvlc {stationsource}".format(
                stationsource=self.current_station['source'])
        self.playing_process = subprocess.Popen(
            play_command,
            shell=True,
            preexec_fn=os.setsid)
        self._is_playing = True
        self.update_display()

    def stop(self):
        """Stops the current radio station."""
        print("Stopping radio.")
        os.killpg(self.playing_process.pid, signal.SIGTERM)
        self._is_playing = False
        self.update_playing()

    def change_station(self, new_station_index):
        """Change the station index."""
        was_playing = self.playing
        if was_playing:
            self.stop()
        self.current_station_index = new_station_index % len(STATIONS)
        if was_playing:
            self.play()

    def next_station(self, event=None):
        self.change_station(self.current_station_index + 1)

    def previous_station(self, event=None):
        self.change_station(self.current_station_index - 1)

    def update_display(self):
        self.update_station()
        self.update_playing()

    def update_playing(self):
        """Updated the playing status."""

        if self.playing:
            lcd_message_at("playing",1)
        else:
            lcd_message_at("pause",1)

    def update_station(self):
        """Updates the station status."""
        message = self.current_station['name'].ljust(LCD_WIDTH-1)
        lcd_message_at(message,2)

    def toggle_playing(self, event=None):
        if self.playing:
            self.stop()
        else:
            self.play()

    def close(self):
        self.stop()
        lcd_message_at("Radio uit",1)
        lcd_message_at("Wacht op LED",2)


def radio_preset_switch(event):
    global radio
    radio.change_station(event.pin_num)

if __name__ == "__main__":

    global radio
    radio = Radio()
    radio.play()

    global end_barrier
    end_barrier = Barrier(2)
 
    nextstation.when_pressed = radio.next_station
    prevstation.when_pressed = radio.previous_station
    playpause.when_pressed =radio.toggle_playing 
    playpause.when_held = end_barrier.wait 
 
    end_barrier.wait()

    radio.close()
    call('sudo shutdown -h now', shell=True)

strangely, after routing audio to card 1 which is the usb card and setting the FS readonly, sound comes from hdmi monitor. Setting it to card 2 in alsa-conf, being the hdmi monitor, causes sound to come from hdmi monitor before setting the filesystem to overlay/readonly, but from the usb sound card after setting filesystem to readonly. So that's how it is used now, as in daily use there is no hdmi connected.

Also, I use gpiozero instead of the original 'button listener' . And since mplayer is not included in the current raspberry Pi OS, I use VLC.