~ $ md5sum /boot/*4*
there is my list, its prob a mix of your release and the github firmware latest.
I really tried everything, but the audio would not fix.
This combo boots all the way, and is a bit faster I thought than the 1.5 original files,( but i might be wrong
I could have messed up something I don't understand
just a note
I had also booted just your 1.5 files, but to boot I had to comment out the fkms line in config.txt
with only your files it still had audio cut outs in the youtube videos.
Im also using the fan shim, I edited the installer to install the service to init.d (openrc) so the lights and fan work and turn on and off.
could you upload your fan shim files to the your github,as i guess you made them run (edited) in openrc, it may be a help for people that dont understand how to fix it to work. I think mine is fine but not totally sure, I didnt edit everything, just enough to install the service