Thanks for these insights! Gigabit is of secondary priority at the moment, just a nice to have. Maybe in the future I would break things up even more and have a dedicated firewall with minimal resources, then this machine I am planning on getting now would be a dedicated OpenBSD based server for proxying, load balancing, etc (basically everything I can do easily on OpenBSD without docker) and finally I would also have a stronger box for several docker services.

Wouldn’t there generally be a significant power draw difference between an SFF and a smaller (micro, mini, SBC…) machine?

Nice!

The only smart appliances I have ATM are smart light bulbs. These also partially contribute to saving energy (eg turn off lights when nobody is home / in the room), but even if that is not your priority, you can set up nice automations to soften the light as it becomes darker. I also use HA with Rhasspy to voice-control the lights.

As for fridge contents tracking, I wish there was a usable solution to what you describe. I have tried Grocy (can be integrated with HA), which looked nice, but I eventually stopped as it took a really long time to maintain. After each shopping, I had to input everything I bought (almost an hour usually). Then, each time you use something (eat a bun with some cheese, finish a bottle of milk, open a new sachet of some seasoning, etc), you must ‘consume’ it in Grocy. 99% of the time I forgot or was too lazy (once again, it just takes too much effort) and therefore the stock database was always out of date, making the whole thing useless.

Other things: I haven’t tried yet, but I also want to acquire some cheap sensors for temperature, and perhaps other things that I can’t think of right now. Maybe turn on the AC for a bit when it gets too warm (and somebody is in the room)?