Thanks for putting these up.
I’ve tried a few wireless “solutions” in the past and ended up giving up. Often good signal between the transmitter and receiver are great with no-one around, but as soon as the pesky Karen’s and Keith’s of the world start standing, walking or dancing in the line of sight between the TX and the RX then the signal has to hope for reflected, rather than direct signal.
Since reflected signals have to travel greater distances that direct, as they’re bouncing off of the walls, ceiling etc, their 50m range in used up “in the bounce” , reducing the range badly.
Longer antenna on both the TX and RX units can help see around obstacles, but these pocket devices don’t appear to have any antenna, unless they use the usb lead you mentioned as a combined charger/antenna lead.
I might consider these for cordless headphone adaptation, although I doubt headphones put out enough signal to work these, but id be reluctant to use these for main audio