Add this to your advancedsettings.xml file:
<!-- Stop Music OSD from disappearing for 2 hours -->
Found the location of the file -
LibreELEC:~ # find / -xdev -name advancedsettings.xml
As the log says, that's a read-only file.
You'll need to make a new advancedsettings.xml and stick it in /storage/.kodi/userdata (or edit the one you've already put there).