I once bought a router to use for my internet when I moved into my new house just to find out that it “wasn’t compatible” with Verizon’s service. I still have it (because I’m terrible about returning things). Is there any point in keeping it? Is there anything fun or interesting that I could do with it?
Official guidance from Verizon is you can use your own router as a router, by setting your Verizon router as a modem only, then connecting it to the WAN port on your router. See e.g. https://kb.netgear.com/31100/How-do-I-set-up-my-Orbi-system-to-work-with-Fios
Unofficially, it’s fine. You can just use your router. The modem is in the white box on the wall (the ONT) with fibre on one end and ethernet on the other. I’ve been running my router directly to the ONT for 3 years without issue. It just works fine.