How to Change NAT Type F to Something Useable?

Hello.

I am trying to play a game on my Nintendo Switch Lite online, but I keep getting Error Code 2618-0201 (a communication error) every time I attempt to connect online despite being able to see which of my friends are online, visit the EShop, and having a working WiFi connection.

By following Nintendo's own Customer Support steps (https://en-americas-support.nintendo.com/app/answers/detail/a_id/25866/), I have determined the NAT to be the most likely issue as the situation has not resolved at ANY step in the process through multiple attempts on different days. My modem-router will not recognize the Switch as anything other than an "unknown device", either, and setting up a static DHCP has not appeared to do anything to resolve this. The Switch is in the same room as the modem-router and the modem-router is an updated model, new, and unobstructed by anything that could interfere with the signal.

This has become extremely frustrating as I am paying both for decent WiFi from Comcast and for Nintendo Online.

How do you change NAT types (A or B is recommended as the best setting for Switches according to my research)? Does anyone else have this same issue?