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?
"Not Compatible" usually just means "We're extracting a monthly fee from you to use out provided router". Most likely, if you were to poke around, you could turn your ISP router/modem into a dumb modem and disable the inbuilt router, then connect your (better) wifi router to that.
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.
Potentially you could serve them a captive portal. I thought about this a while back, basically to create a sneakernet WiFi network where people could connect directly to a landing page that had my music for download, for example.
If you have anywhere in your home with poor Wi-Fi signal, you could set up the router in bridge mode to effectively act as a range extender. Just make sure to disable DHCP on the 2nd router or it will wreak havoc!
I did this with my old router and as others have said it effectively cuts throughput in half. Depending on your usage though it might not be a big deal. I only connected mine so I could get a signal in the front yard. It's fine for surfing the web or watching YouTube
When I upgraded to a mesh system a while back, I turned my old router into a dedicated access point just for playing VR games wirelessly on my PC. Performance improved noticably once it didn't have to compete with the regular house WiFi traffic.
I assume you had a hardline from the VR router to the central router? Otherwise wouldn't the wireless communication between the VR router and the central router be in the same competition as the VR headset was before?
Most/all of the data transfer in their case wouldn't be hitting the regular router; the spare router would only be acting as a go-between from the PC to the VR headset
Custom firmware like tomato or ddwrt can be fun to just play around with and learn more about networking. I used my old router temporarily as both a wifi repeater and as a wifi receiver using custom firmware. I didn’t need it for any particular function, but it was fun to experiment with
I just don't fully trust the ISP router, so I disabled the wifi and hooked it up to my own router. If the ISP router gets hacked, my internal network doesn't get exposed.
Port forwarding is a bit harder, but you probably aren't even doing that at all (and it still works anyway, it's just an extra step).
That's an interesting idea. How do you access the router connected to the ISP to setup port forwarding to your second router? If it's too complicated to type out here, I'll understand.
If you're not going to hook it up to the internet (bridging, access point, etc.), name it something funny or provocative for the neighbors.
For example, I live in a college student neighborhood with a lot of Chinese students. I have an old router that I'm going to use the network name 六四屠殺 which is Chinese for the June Fourth Massacre (the Tiananmen Square Massacre). It's a term banned on the Chinese internet.
Mesh/range extenders really suck terribly, and that cannot be overstated. If you do any streaming or gaming or video calls, don't do that on mesh APs or range extenders. Especially if you live near other people.
You could probably turn it into an extended access point or something like that. You could also set it up to be used in like let's say a lab or something like that. If possible, check what router it is and see if you can put OpenWrt or something like that on it.
If not, collecting dust in a box isn't a bad idea either, just if you decide to take it out again to clean it thoroughly.