ESP-NOW sync message is currently transmitted on the same channel as connected WiFi.

This will prevent other nodes, not connected to WiFi and not using the same channel (currently 1 when in AP mode or unconnected) from receiving ESP-NOW messages.

It would be much better to broadcast ESP-NOW messages on a predetermined (possibly user selectable) channel instead of the channel used by WiFi.

This might require temporarily disconnecting WiFi, sending ESP-NOW message and reconnecting WiFi.

As transmitting ESP-NOW message may take some time, it will be mandatory to prevent automatic reconnection of WiFi from WLED loop().

The unfortunate side effect will be diconnection of websockets clients. The benefit will be that you can easily use mobile WLED units that stay in sync with master regardless of being connected to WiFi or not.