I managed to maintain 9 simultaneous BLE conexions, enable the notifications for the specific characteristic im interested in.

Receive all notifications and decode the bytes in the payload

The gatttool doesnt allow me to connect a 10th BLE device, i feel the bluetooth chip really struggling when opening more than 5 BLE conections, this would not happen with a raspberryPi4 (different more powerfull wirelles chip) or a raspberryPi3 without active wifi conections