It's up to you to make it cloudless, but Home Assistant is the only solution I know of out there that even allows this possibility. I refuse to use anything in my home that requires a third party app or cloud connection (aside from initial pairing so I can flash it with ESPHome or some other local-only firmware). Admittedly it complicates things, but the payoff is so worth it.
Even well-intended messages can be suffocating. All it takes is an explosion in popularity due to circumstances outside your control (like we're seeing here), and suddenly you're inundated with GitHub issues, PRs, conversations, important decisions, critical incidents that need a response and so on. Even if you're full-time on it and salaried (which most open source devs aren't), you simply can't keep up with the volume - dozens, hundreds or thousands of other contributors trying to contact you, debating every aspect of your decisions, technical and social. The toll on mental health can be significant, especially to those personalities who like to stay organised and on top of things.
Similar story here, it's a great idea until it goes wrong, then you've got two appliances down instead of one.
My Home Assistant instance has become so mission critical to my household that I've got a dedicated Pi 4 for it, with a fallback Pi 4 and preflashed SD card ready to hot swap and restore from backup.
This is a feature, not a bug. But we definitely need a solution to make subscribing/coalescing them easier for users. Mastodon allows subscribing to topics (hashtags) - I think something similar is needed here, but that will evolve naturally over time.
It's up to you to make it cloudless, but Home Assistant is the only solution I know of out there that even allows this possibility. I refuse to use anything in my home that requires a third party app or cloud connection (aside from initial pairing so I can flash it with ESPHome or some other local-only firmware). Admittedly it complicates things, but the payoff is so worth it.