Backup DC power standardization with Photovoltiac battery systems?

Are broadband CPE (ONTs, CMs, NIDs, etc) manufacturers and PV battery wall engineers working on any standardized CPE backup power connectors? AC/DC/AC & wall wart DC again is inefficient and reduces runtime. It would be nice if PV/DC battery wall and broadband CPE had a standard DC connector instead of the incompatible hacky/proprietary used now. A DC bus would be nice, but even the EU regulatory approach of requring a USB-C power connector on ONTs and Cable Modems would be a start. All these darn wall warts are almost, but slightly different (5v, 12v, 24v). No -48v CPE? I have enough EE knowledge to build magic DC boxes, but I would prefer a good UL-listed interoperable solution.