Hi, we just updated the code for gsmMuxd.. and you no longer should need the n_gsm kernel, and you can compile the gsmMuxd driver under a 64 bit OS.
The guide has also been updated https:/ozzmaker.com/how-to-enable-multiplexing-on-the-raspberry-pi-serial-interface/
The serial should work even if you haven’t enabled multiplexing. Does the PiSugar also use the serial connection on the Pi?
Richard --OzzMaker.com --