After having my server fail to recover after a power failure while I was out of town for an extended period, I moved all important server apps to an relatively inexpensive (<$200) laptop.
The battery is firmware limited to a 70% charge which means it will last for years with no significant safety concerns. Even at a partial charge, Debian indicates 7 hours of run time when the power fails (I’ve had none longer than 4), and it’s unaffected by power blinks. It saves a bit of electricity too and costs $150 less per year to run than my old UPS alone.
It’s been running for nearly 2 years without a hitch.



Your assumptions are no longer accurate.
For one thing Lithium-ion batteries are becoming common in consumer UPS models including those from Cyberpower, Eaton, and APC.
There is no memory effect and they don’t need to be discharged and recharged regularly.
The risk of fire is extremely low. For a high quality charge limited lithium ion battery in a controlled environment it is about the same as a UPS with lead acid batteries.
Battery swelling (not caused by manufacturing defects) is primarily caused by overcharging, deep-discharge, physical damage, and heat, none of which are problems for my server installation.
The risk of fire from parking your car in your garage is hundreds of times higher than using a laptop as a server.