I have 3 Wii U Pad Pro for multiplayers gaming. And I wasn't able to pair a third paddle on my new X64 laptop. I fixed this issue with the bluetoothctl command tool.
Before starting, pair separatly all you pads with Batocera to get its ID in the bluetooth database. You'll needs their ID to operate.
Open a remote session on your Batocera via SSL and type this command : bluetoothctl devices
It shows you all scanned bluetooth devices. Like this :
# bluetoothctl devices
[NEW] Controller 00:1A:7D:DA:71:03 BlueZ 5.47 [default]
[NEW] Device 7C:BB:8A:0A:7B:1D Nintendo RVL-CNT-01-UC
[NEW] Device 7C:BB:8A:1F:63:14 Nintendo RVL-CNT-01-UC
[NEW] Device 7C:BB:8A:1D:C9:35 Nintendo RVL-CNT-01-UC
[NEW] Device 5C:BA:37:C6:D5:92 Xbox Wireless Controller
[NEW] Device 2C:41:A1:23:7B:5F LE-Bose Revolve+ SoundLink
Take notes about your Wii U Pad Pro ID. For me they're :
For each Nintendo devices, you have to (one by one) type this commands :
Of course, don't forget to press the small red sync button behind your gamepad, before execute the pair command. Otherwise it'll not pair.
The trust command is usefull to make you're gamepad ready for auto-detect. This means, next time you want play, you just have to press the A button on your gamepad, and your Wii U Pad Pro will link automatically with Batocera.
Hope this will help you.