The connection between the ONT/PON/GPON and a router is made using a CAT5e or better LAN cable.
Provided you have your connection username (ending in @broadband.vodafone.co.uk) and password, and can express the correct VLAN ID - usually 911 - on the router WAN port, then any decent router should do.
The more complex your network, and the greater the number of devices you are using, the more powerful a router you should be picking. But if the supplied THG3000 does everything you actually need, then there would be little point in replacing it!
*The only list of routers I'm aware of in relation to Vodafone is the list of OpenReach approved modem+routers for ADSL & VDSL. That list does not apply to Gigafast and equivalent connections and seems to have lapsed anyhow (last update would have been 3 or 4 years back!).
