For me it's still not working with latest LibreELEC Beta on Pi4 + Yamaha AV-Receiver + LG TV and the Micro HDMI adapter by Pimoroni. Absolutely nothing recognized while working with the same constellation on a Pi2.
Ordered a AmazonBasics Micro HDMI cable (instead of an adapter) now to check if that helps.
UPDATE: Plugged in the Amazon cable and it was running immediately. The Pimoroni adapter was guilty in my case.