I’m still not familiar with this tempting product, known as WONDOM PS-BC12211 but still sharing here as related: “The 2-port USB charger on battery extension board supports USB charging specification, revision 1.2 (BC 1.2) which could automatically config D+ and D- lines connections for an attached device. The battery extension board automatically adjusts its output level based on the connected device. It is compatible with smartphones and tablets from Apple, Samsung and Google. The extension board can charge up to two devices at the same time, which can get more output than ordinary dual-port chargers. A maximum output of 5.25V/2.1 A brings you to a whole new level of high-speed charging.”
WONDOM distributors are well known but this one provides few more pictures of the above presented product, by adding: “USB- Erweiterung für das Wondom BCPB4 5- Zellen Akku- Board. Ermöglicht das High-Speed Laden von mobilen Endgeräten per USB Anschluss und das Laden des Akkus per Rundstecker”.
EDIT/NOTE: By eventually using above linked product or any other USB3.1 or USB3.2 dedicated charging and charging downstream ports, for charging only of the Librem 5, I would recommend (just my non-expert opinion, if not mandatory while might be easily related to the additional heat produced, while still not used/tested in real environment from my side, not up to now) to have USB-A to USB-C cable with integrated 56kΩ pull-up resistor or rather adequate adapter with the originally delivered USB-C to USB-C cable on board: