This specification might be useful.
I’m reading section 2.3.3 and 2.3.4 right now. Section 2.4 is also interesting (VBus). There are links to other documents as well, such as the PD Specification.
Edit: the bottom of page 218 indicates that you can use USB2.0 or USB3.2 if you don’t want to support PD negotiation and monitoring.
Note there are small (12mmx30mm) PD sink modules (with USB C connector) that will supply a fixed voltage and handle
All the negotiation for you. Voltages available from common modules include 5v, 9V, 12V, 15V, and 20V. Let me know if you want me to find a link for you. I’ve ordered them from AliExpress before. They are less than USD $5, if you’re willing to wait 1-2 months for delivery. There are also small (2.5mmx2.5mm with 0.5mm pitch and also smaller) chips as well, but I don’t have experience with those.
Edit 2: this stackexchange post seems a very good summary of power options for a dumb device.