Programmer notes
Mods to WebKit probably in 2019 made it default behaviour on most browsers not to permit file:// to access other file:// URLs. MacOS could work around this by tweaking system preferences (weakens security ?) or by running a local web server, as in this script.
The SFHG USB stick is produced on a Windows machine, which does not preserve the file attribute "Execute". A workaround is to use ZIPping on a Mac, for Windows USB stick production, with the unZIPping done on a Mac.