you can switch the bluetooth-drivers to Shanwan
by editing the batocera.conf file
\\batocera\share\system
when your RPi3 is connected to the network, you can access this folder via file explorer from a PC that is also connected to this network
either via IP or if you just type in the file-browser \\batocera
if you are using windows
-------------- D1 - PS3 Controllers ------------
##Enable PS3 controllers support
controllers.ps3.enabled=1
Choose a driver between bluez, official and shanwan
bluez -> bluez 5 + kernel drivers, support official and shanwan sisaxis
official -> sixad drivers, support official and gasia sisaxis
shanwan -> shanwan drivers, support official and shanwan sisaxis
controllers.ps3.driver=bluez
just replace the "bluez" in the line "controllers.ps3.driver=" with shanwan
and save the file, then reboot and test if your controller works then in dreamcast