Description about Raspberry Pi 4 Model B:
https://forum.pistar.uk/viewtopic.php?t=1906
Download IMG
http://www.pistar.uk/beta/
[Reference blog]
System LED explain and flash image guide
https://mmdvm.bi7jta.org/search/label/Pi-Star_OS
Assemble for Keenwood, plugs and play. Check it out .