My application is using Wi-Fi on boats and cars, so I’d like to use 12 VDC. For example, currently I use a Alfa AP-121U , which has “12V Passive PoE”, but I’d like to use the GL-AR150 because it’s much smaller.
I have used a car type usb supply, a passive poe injector and a micro-usb splitter for this. All the bits are commonly available and allows you to use any GL mini router with the micro-usb power connector. This seems fine on a 20 metre cat 5e cable. For longer runs you might need the usb supply at the router end and push 12 volts up the cable.
The Raspberry Pi market seems to use this approach and all the bits can be found on Amazon.