have been using different routers in the past for this, first i used an ASUS, and then later an Elecom (attached picture)
these came as a consumer good that i stripped and used the board from.
unfortunatly they are kinda hard to come by these days, last time i go 50 directly from a friend in Japan, but he cannot get them from elecom anymore (not produced anymore).
i have tried with a Skylab SKW75 for testing, and it worked, but that one is no longer in production either.
at the same time i tried with a Skylab SKW103, but i had the same problem as i do not with not getting the WAN port to work. (assumed it was just a bad part, since the SKW75 worked)
so decided to try something else

that ended up with the Hi-Link, but ran into the same problem as with the SKW103, so then i must be missing something

i havent played with the PHY LEDS at all yet, only been trying to get the fuctionallity to work, then i will start looking into that. i want to have 3 LEDs, power, link and activity.
no diagrams at all yet, not realy proficient in the different electronics programs, i guess i need to, since if i get this working i plan on getting PCB's made for it.
initially i will most likely just make a couple of prototype boards using fusion360 (yes i know definatly not the right tool)
setup is not complicated thou, it is a special industry connector that holds 24VDC and Ethernet, then wired to a buck converter and then the router. (attached pictures of the finnal tool with Elecom router)