Some have tried working on this. Authentik even developed a hack to make it work with HomeAssistant. Unfortunately the core devs of HomeAssistant have historically viewed external auth as a niche feature that users don’t care about.^[1] Not sure if that is still the case, but until that mentality changes we are stuck with native auth because PRs are just going to get denied.

I think this post pretty much sums it up:

In 2024, Home Assistant sticks out like a sore thumb among FOSS projects for its lack of modern authentication and authorization.

Through a faraday cage? I mean, maybe… but have you checked if you can just turn the wifi functionality off on the ISP device? Most will let you do this and it would be way easier/cleaner.