Reddit mentions of Axxess Subaru 2015-Up USB Retention

I upgraded to a Pioneer Nav unit in the fall and I believe that this USB Retention Harness Is what I have to retain the USB in the armrest. Unfortunately, Android Auto didn't work between the Pioneer unit and the S7 for some reason but the USB does work.
Side note: The OEM backup camera also works with using the Axxess AX-SUB28SWC but I recall the wiring was changed in the 2017 so it wasn't color for color as original wiring diagrams went.

That plug is for USB, you can use this adapter to plug that into your new head unit's USB port.

The rearview camera is part of the 28-pin adapter, pins 11-13 (I think), check out the thread here. You can use this 28-pin adapter which includes the 12v to 6v converter to plug in the rear-view camera to an aftermarket head unit instead of buying the add-on unit.

https://www.amazon.com/gp/product/B07GD8627K/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1 this is the harness i used, has the reverse 6v signal already to go. all you need us usb retention https://www.amazon.com/gp/product/B01DJ4KVQ6/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

then the speaker harness. https://www.amazon.com/gp/product/B0002BEQJ8/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

and lastly the antenna harness https://www.amazon.com/gp/product/B003VYWSES/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

these were all the things i used to wire in my kenwood. besides the tool to keep steering wheel buttons https://www.amazon.com/gp/product/B00J4W10XG/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

the autoharnesshouse harness makes it easy to use the maestro by the way. hope this helped. i have a 2017 wrx by the way so i dont know if there is a difference with 2015 and the new 2018+s

Yes I got an adapter that allows me to use the center consoles USB port. Axxess AX-SUBUSB2 USB Retention... https://www.amazon.com/dp/B01DJ4KVQ6?ref=ppx_pop_mob_ap_share