My speakers are connected via USB-C and work perfectly. I therefore cannot judge whether a connection with a 3-pin cable works.

Oh dear, please contact us if there are any missing items: https://www.digitec.ch/help

Must be possible: I just plugged their USB-C cable to a multiple-USB-C power socket, and it works (sound streaming on Bluetooth). - it frees a USB-C port on the Mac - apparently, you can send sound to the Pebble (Bluetooth) *and* Airplay speakers at the same time after setting in the Midi Audio Setup utility. But you can't stream to Pebble (BT) and Sonos speakers simultaneously.

The manufacturer has not provided this information, but theoretically, if both devices (player and speaker) are Bluetooth 5.0, they should hold the connection to ~240 metres in open space, but of course this is not often seen in real-world usage scenarios

I assume that you are referring to the following product: https://www.digitec.ch/de/s1/product/creative-pebble-pro-20-usb-c-pc-lautsprecher-mit-bluetooth-bluetooth-lautsprecher-24142177. We were recently able to add this to our range via a third-party supplier.