widening the topic to the future life of this cluster in such a scenario, I have a general plan for that as well:

* use 35-watt tier (T-class CPU) #1LPC systems for now, with an eye to moving to 15-watt tier (U-class CPU) systems in another couple upgrade cycles; currently there isn't really a U-class equivalent of the T-class #TinyMiniMicro systems from the big manufacturers, NUC is about as standard as it gets.

* develop technique with gear on hand whenever possible, meaning continue using these ancient & crappy consumer UPSes with drop-in LFP batteries, use existing 15yo RasPi for control, but the point is to have the experience built up so I can quickly switch to a Pi Zero class system and a custom DC-DC UPS when the time comes.

@hacksilon @foxbasealpha Yup, strongly recommend this approach as well. Raspberry Foundation have just announced a fresh round of price increases due to AI stupidity and the 8GB models are increasing by $50 ...

I'd personally look on ebay or similar for an old #TinyMiniMicro device (https://www.servethehome.com/introducing-project-tinyminimicro-home-lab-revolution/) and run Home Assistant on that, either natively, or in a Proxmox VM (my personal solution).