From the Compatibility page:

“The initial PQConnect software release is for Linux. The software installation relies on packages supplied by Linux distributions. Package names are not synchronized across Linux distributions. The installation currently understands the names for Debian; Debian derivatives such as Ubuntu and Raspbian; Arch; and Gentoo. Adding further distributions should be easy. [The installation also requires root access.]

“Support for non-Linux operating systems is planned, handling the different mechanisms that different operating systems provide for reading and writing IP-layer packets. The PQConnect system as a whole is designed to be compatible with any operating system. The PQConnect software is written in Python. The underlying C libraries for cryptography have already been ported to MacOS.

“Accessing the IP layer is not the only way to implement the PQConnect protocol. Existing user-level applications access the kernel's network stack via system calls, normally via libc. It is possible to modify those network packets by modifying the kernel, by modifying libc, or by pre-loading a PQConnect dynamic library, still without touching the individual applications. […]”

I would have expected information about OS support, and on which application/OS layer PQConnect operates, on the Intro page.