This is possible in GrapheneOS and is super nice. I use a keyboard app that I like but disable network access to ensure that it doesn't send private data anywhere.
But it's not very useful in practice: if an application doesn't need networking for its core functionality, then there usually is an open-source equivalent that does not use the network in the first place. The few applications that lack a good open-source equivalent (public transportation, proprietary messaging protocols, banking) don't do anything useful without network access.
What would be more useful, however, would be the ability to selectively block network connections: for example, to allow the public transportation app to access its API endpoint, but not the advertising and tracking endpoints. I don't think LineageOS allows that, and I don't know if Graphene does.