Librem 5 does not support QC protocols (especially when Qualcomm® Quick Charge™ technology not translated wrongly).
For our interest here, this document is very important initial document (prior to recent ones, and latest one defining PD3.1), let me sort it as historical one, official one that belongs to this thread: https://www.usb.org/sites/default/files/USB_Type-C_Compliance_Document_rev_1_2.pdf. It defines our environment. Therefore please go back to this post:
Some good PD orientation link (with important table): https://www.pshinecable.com/article/what-are-the-differences-between-usb-pd3-1-and-usb-pd2-0-pd3-0.html.
On the other side following document belongs to this thread only partially (USB-IF certified controllers related) and therefore not belonging in general to the Librem 5 category: https://www.qualcomm.com/content/dam/qcomm-martech/dm-assets/documents/quick-charge-device-list.pdf. Anyway, this document is for certain important as very present in our modern, technical surrounding.
P.S. No unnecessary comments of mine this evening (I hope). And might post this weekend some photo of QC3.0 charging typical Android smartphone. Also, as almost certain, your USB gadget is actually dedicated QC charging protocol tester (support for QC2.0, QC3.0 charging protocols is broad/mature one).