Selfhosted

You lost a bit of credibility when you misspelt atoms

There is more than one type of water, but unless your IoT device is a fusion reactor it's probably just running off the normal blend.

Right, but none of them are new. They've all been around for billions of years.

KNX.

Everything is decentrally programmed, and you can do extra automations and stuff from home assistant, but KNX devices are wired (generally) and will always Just Work™. More expensive that the cheaper retrofit options, but if you factor in manual overrides or getting the "better" wireless smart devices it is comparable. They generally also have a manual override at the panel. For core functions like lights, HVAC, roll shutters or blinds, etc... That is honestly the best option (unless you want every light to be an RGB light for some reason, then you still need smart bulbs)

That's a great rule of thumb. So setup two switches. One for manual and one with a ESP32.

I've watched enough Lock Picking Lawyer never to want a consumer 'smart lock.' Half of them can be opened with a magnet. Maybe commercial grade is better, but I've been locked out of my job after every power failure for the last 10 years, until someone comes along with a physical key.

Re homeassistant on a Pi: homeassistant does a lot of database transactions, so you may want to have db storage on something other than an SD card.

I wish I had setup an identity management system sooner. Been self-hosting for years and about a year ago took the full plunge into setting up all my services behind Authentik. Its a game changer not having to deal with all the usernames and passwords.

In a similar vein, before Authentik, I used Vaultwarden to manage all my credentials. That was also a huge game changer with my significant other. Being able to have them setup their own account and then share credentials as an organization is super handy.

ZigBee router thing:

I've been happy with the SMLIGHT SLZB-06M. You can easily flash firmware, and it has PoE which was important for me. I believe it also supports Thread, but I haven't tried this yet (and I'm not sure if it supports it at the same time as Zigbee).

Zigbee smart plugs from Third Reality have been pretty solid in my experience, and they report power usage.

For circuit breaker level monitoring, I have an Emporia Vue2. I have it running esphome, completely local

unfortunately this requires some simple soldering and flashing, so it's not turnkey. But it's been rock solid ever since flashing it. (Process is well documented online.)

I've had decent luck with cheap wifi Matter bulbs, but provisioning them is finicky, and sometimes they just crap out and need to be power cycled; Zigbee bulbs (e.g., Ikea) have generally been reliable, though sometimes I've had difficulty pairing them initially. After power cycling a Matter WiFi bulb, it takes a while for it to respond to Home Assistant; Zigbee bulbs generally respond as soon as you power them on.

I have a wired smart light switch from TP-Link/Kasa (KS205), and it's been completely hassle free (and totally local

Matter over wifi). The Kasa smart switch dongles I have work flawlessly but need proprietary pairing, and I'm afraid to update firmware in case they lose local support.

Good luck! Fun adventure :)

if you have a garage, design a method to basically ensure your garage door is closed without you needing to go back to check.

of course if you trust yourself with never making that mistake.

last thing you want to feel is if you remembered to close the door or not and youre already far off

Cameras.

Dehydrate you