I can't speak for the GL.inet devices, power is going to be your biggest woe, but I have used both Y connectors as Belkin PD powered Ethernet, I've had luck with both but the former (Y splitter in conjunction with RPI) seemed to have conked out over time. And the ability to power the device is also very inconsistent. Since you're trying to connect it to WAN port, I recommend the Belkin PD Powered Ethernet device. And you'll want a nice power supply for the type-c PD port on it. I'm using a 65W GaN charger. The charger that came with M2000 is inadequate.

I have the Belkin ethernet connector connected to the WAN port of a router that acts as another gateway device in my existing network.

I was googling for power adapter for my new Pinecil, and found this post.

I do have the adapter OP posted: ULTRANET 65W

Problem is that Pinecil constantly triggers overload protection on it, and it keeps power-cycling the Pinecil.

/edit Changed to a beefier cable, and now Pinecil works fine. So, never mind. :) Charging my Dell Inspiron laptop over USB-C. It's complaining about a slow charger, but charging. :)

I connected it through USB-C power meter tester and it works fine, showing up to 53W getting pulled.

Buyer beware - you may have problem powering Pinecil with ULTRANET.

I'm gonna order the Nekteck 60W and try that.