After playing with this quite a bit, I discovered that the controller becomes active as soon as the right trigger button is pressed. This seems very strange, but at least I know how to work with it.

came across this thread on google searching for a solution to the same problem.
This thread's answer didn't work for me, unfortunately,
but updating the bluetooth driver did work for me.

sudo apt install pi-bluetooth

good luck to anyone else passing by with DS4 connectivity issues!

@CobraKai I have not, but it looks like the xow driver is only for use with the Xbox wireless dongle. (I think it only references bluetooth on the 'supported devices' frame to differentiate it from the the other models)

That's what I call an all-encompassing answer ;-)
Thanks a lot mitu.

Actually, you can't even manually change the config file. It seems that jstest & emulationsation interpret one button as "0" but retroarch interprets that same button as "3". So yeah, you can fix button 10 by changing the config file to say "7" but retroarch doesn't like buttons to have negative numbers assigned so this doesn't work as a long term solution.

Many will say "buy a different controller." The Amazon is so far away. Also, the cost-benefit analysis of using a pi and retropie compared to buying something like the Allcade was that I wouldn't be needlessly buying things that I already had!

How is the process for creating the controllers udev? I'm unfamiliar if you care to share.

So Iv'e been working on it and got the drivers to install from source and the BT paired. The controler worked via BT in the retropie setup, as soon as i exited it crashed the system. I rebooted and paired again , rumble scan pair, CRASH...

@smoothmalik If bluetoothct1 is not present, it means retropie is still using BlueZ 4, to my knowledge you won't be able to run both PS3 and PS4 controllers at the same time with this kind of setup. Perhaps you should open an issue about that on retropie's github

I have a controller name as "SHENGHIC 2009/0708ZXW-V1Inc. PLAYSTATION(R)3Conteroller " too.
Have tried it with the retropie 4.5.18 with sixaxis driver (third-party), ps3controller driver(both gasia and shanwan ) or even xboxdrv, neither of them works.