Seems like your best bet is to use an industrial battery inverter/charger system (Victron Multiplus) for slow-switching (>20ms) and then layer a secondary indus

Seems like your best bet is to use an industrial battery inverter/charger system (Victron Multiplus) for slow-switching (>20ms) and then layer a secondary industrial grade UPS to provide fast switching (<15ms) and shutdown process through USB/serial/network etc. Is it cheap? No, but you shouldn't be using cheap power supplies to protect your more expensive server equipment.