I just bought joying Unit for my forester xt with harman kardon. It works perfectly. You need to make sure the wire to power the amp on is in the right location. On my car is the blue wire on the car harness. The harness that came from Joying was wired on the wrong location. This is my second android head unit, and I am very impressed with it. I upgraded from an px5 to this one. I opted for 8 gb of ram and 128 of internal storage.After a lot of reviews and reading I just ordered a 9" Idoing with CanBus for my 2018 WRX with Harman Kardon. A lot of positive reviews from WRX owners, but not seeing a lot of love(or hate) for the Idoing hear on XDA. It's nearly identical to the Joying, but Joying will not support the HK system in my car.
The system is an android 10, UIS 7862 4+64. https://www.aliexpress.com/item/32955093508.html
I'm curious what custom options I have in terms of UI, ROMs, Root,, apps?
I'm guessing from what I read(or lack there of) ROMs are a no go, but what about root and other customization options?
Sorry long time rooter and custom ROM user for android phones and tablets, but total noob to android head units.
I have a Kenwood with wireless android auto in my old car and was going to move it to this one, but absolutely hate Android Auto almost as much as I hate mirrorlink in the stock HU in my WRX(shame on you subaru). Also the kit to install it from crutchfield cost nearly as much as the android unit and canbus shipped from china, so figured i'd take a chance.
If it doesn't work out I'll go with the kenwood, but really hopeful this will be a winner. I spent a lot of time on chat with them and they are extremely responsive to questions(really like live chat) where a question to Joying took 3 days to get a response.
I know there is little chance the 4G module will work in the US(IDoing says it works with tmobile) so expecting to use wifi tether with my phone with native apps and pretend android auto doesn't exist. Other option is put a spare phone with sim permanently connected to USB, but unsure if USB tether will work.
I will keep reading, but any thoughts or pointers are welcome. Just don't tell me to replace my HK system, I know not everyone likes it, but I love it ;-)

2013-2015 Subaru Forester Android 10.0 Car Sound System Head Unit With IPS 1280X800 Screen
SKU: JY-SQ002N4G-BShip From: Chinese WarehouseCPU: UIS7862 12nm Dual ARM Cortex-A75 + Six ARM A55Ram: LPDDR4 4GB Rom:EMMC 64GBSupport Bluetooth, WiFi, DVR, OBD2, Back-Up Camera
