I compiled the latest ffmpeg source with the (adjusted) patch from the NG back in April (your link in the OP). I got the same result that AF did (his post 6 April 20:46).

ffmpeg recognises the stream and starts copying it

Stream #0:0 -> #0:0 (flac (native) -> flac (native))

but immediately stops.

Looking inside Firefox I can see that the actual sound is in a continuous serious of numbered 'chunks' with addresses like this:
https://vs-dash-ww-rd-live.bbcfmt.hs.llnwd.net/al/lossless/A1/390659324.m4s
These files only exist momentarily, and when I tried to catch one it was a 404.

So I think that patch adds the demuxer OK, but doesn't address the streaming process.

If you see any further patches mentioned, I'll have another go.