I originally had the 5" and upgraded to the 8.4, so Im not sure exactly what you would need. I do know it would take some creativity to make work because the wiring harnesses arent exactly the same when going from the stock system to the alpine with regards to the amp and sub.
You can use it. I have the wiring diagrams for both systems so I was going to mirror the stock alpine upgrade. If just using the sub you could wire it up with an aftermarket amp if you went that route. Hope this helps, let me know if you need the diagrams and I can email them to you.
Here is a...
Hey fellow quarantined members-
I bought this months back with intentions of upgrading existing speakers in my jlu sport. Now my hours are cut and this project is cut. Everything is like new.
1 Factory Amp, factory Alpine speakers and 10" sub. All out of a 2018 JLUR $500 shipped