As you dropped TV service, you can use any router you like. Verizon support will end at the ONT, but for anyone reasonably techy, that's not a problem.
If the G1100 was working for you, no need to replace it unless Verizon is going to charge you for it. While getting a bit old, it's still supported by Verizon and is a reasonable 802.11ac router. It probably will go out of support in the near future, as Verizon currently has three router models. Once it goes out of support, it will make sense to remove it from service as it won't get any firmware updates, including security patches. But they haven't cut it off yet.
If you like the G1100, you can buy used ones for about $40.
And EDG1's suggestion to turn off SON on the G3100 is spot on.
As for non-Verizon routers to use with fios, it really boils down your budget, needs and desired features. For example, if you want an easy to deploy WiFi6 mesh network to give great WiFi everywhere in your home, Amazon, Google, Netgear and TP-Link products are great ones to look at. Read reviews and specs to find one that looks good for your needs. You can get a basic router for around $50 that will work just fine for a small area, or you can spend hundreds on a multi-node tri-band mesh system. Whatever you do, buy from a vendor with an acceptable return policy in case you find issues after testing in your home.
