I don't think the cellular network is the problem at all - everything except SMS and PSTN calls works on wifi. The problem is the apps. Netflix only runs on a verified bona fide electrified six car Google- or Apple-approved device; so do most financial apps (EU law requires them to) and basically everything else where the app developers are trying to get money off you (which is most apps). Some apps will refuse to play ads on a non-genuine device and then refuse to function because you aren't watching ads. Play Store does its best to stop you installing its apps on a nongenuine device, but it has to support older devices without TPMs so it's not fully locked down yet. Even YouTube has some level of attestation.
In the US at least, you could already have a lot of trouble with Wi-Fi calling when using unlocked Android phones. And it is basically nonexistent if you use a phone purchased outsiden US.