As with all prototyping tools, as long as you have a public share link to test, you can use ProtoPie when doing an unmoderated or moderated study.
This article will discuss sharing ProtoPie links, as well as provide help for scaling, touch points, etc:
https://blog.protopie.io/sharing-custom-pie-links-as-easy-as-pie-72a80f8f213b
Share links can be created in ProtoPie as shown here:
How to open the “share with display options” menu
Click on the Options menu right next to the Pie’s owner name and select “Share with display options”:
A window will pop up with several display options you can choose and the associated customized shareable link. Below is a list of all available options and what they can do.