Let's try: https://github.com/boomzillawtf/nodebb-plugin-youtube-embed#readme
plugin was forked from nodebb-plugin-youtube-lite.
After installation restart and refresh browser or clear browser cache - CTRL + F5
To expand on this, you can reset more than plugins!
./nodebb reset -t restores the Persona theme. You can specify a theme name to switch to that theme.
Looks like we should be using https://schema.org/breadcrumb instead anyways. These attributes only exist for search engine robots anyways, I don't know why Firefox is complaining.
@mgm-ivr what line of code?