Requires rtmpdump with K-S-V patches https://github.com/K-S-V/Scripts/releases/tag/v2.4 to add to the environment variable, add a streamlinkrc file (%Appdata%) or replace it in ...\Streamlink\rtmpdump\rtmpdump.exe
Many thanks!!
It's a shame it doesn't run under Linux... I'll keep trying! :-)