Lovelace and firefox

I was playing with Lovelace in Firefox (60.2.1esr 64bit) and as per the lovelace page I set dom.webcomponents.customelements.enabled and dom.webcomponents.shadowdom.enabled to true

This appeared to break HA. Not just the Lovelace view, the regular UI as well. The view got completely scrambled and became unusable. Setting the two items back to the defaults false cleared it right up. Lovelace seems to run fine though I’ve not tried custom cards yet.

Figured I’d report this here, since the advice on the page seems to be incorrect.

Also having this issue in Firefox Quantum, version 60.2.0esr