Personally I've ordered a Zgemma H52S which appears to offer a decent all round experience. As I only use the N-TV sub I to as a backup to my satellite system and smart tv playlist I thought I might as well get a box that appears to do the lot and also has h265 decoding as a little extra future-proofing should it be needed. £100 delivered and £15 move than a H2S so worth a punt IMO.
Like piggzy says though, android box should do the trick just as well and is probably the cheapest option. Next up would be Roku sticks/boxes but you're back in that ecosysyem and open to possible blocks on the roku platform if enough prssure can be applied by content rights holders.
Depending on how many different update servers the N-TV can connect to, I would expect that using the firewall rules in your router you should be able to block each update server. Possibly something like wireshark to sniff the actual address(es). Not tried it myself but then again I've not switch my N-TV on for weeks.
Read elsewhere that the changing of the servers per vids is more related to the store and general operation of the box rather than the update servers which appear to buried deeper and why some people are still getting updated despite changing server in the menu or disabling network pings.