This is mostly what I do for “critical” Pi things. The cable Ethernet and the SSD are major. Do you have any recommendations for a cheap UPS? What are your considerations here?
I went with a CyberPower BR1200 which was about 150 pounds (circa 200 USD) but that's overkill because it will keep my pi+router going for several hours, whereas power-downs typically last less than 15 minutes max where I live and I haven't seen > 1 hour in 10 years. It's usually "human error" related someone plugs the vacuum in or some appliance trips a circuit. Keeping the router on the UPS (and fiber box in my case) is important though because then everything is completely uninterrupted from a serving perspective. I also give the standard RPI power adapter enough headroom by not overclocking the pi, because in the past this has caused problems when SSD attached with lots of writing, and "big" (for a pi) compute load at the same time. Since turning off the overclocking, zero problems. Probably an RPI5-class power supply would be even better. No clue if this matters but on a jetson nano (which was notoriously power-spikey), crucial (micron) or samsung SSDs tended to be better than budget alternatives.
