Bluetooth LE/ 4 is different from traditional Bluetooth serial port profiles and old instructions don't work. Bluetooth LE is basically all user mode, and there are some instructions on accessing LE devices with gatttool one you find the device address and UUID etc.
I can connect to a TI CC2541 Bluetooth 4 serial port module with gatttool -I and see a hex dump of characters when the module receives data. There are some docs that show how to send raw characters as well though I haven't tested sending yet.
Since this is usermode, a pty could be used to provide a serial port microcom/picom. Is there a way to run gatttool on a pty or socket, maybe use socat for the pty? PyGatt looks interesting as a possible wrapper for gatttool.