On your web site at https://100r.co/site/uxn.html it says:

MACOS. For now, the only way to get the Uxn emulator running on OS X is to build it from the source files, which means cloning or downloading the repository on Sourcehut and writing .build.sh.

First, please change both "MACOS" and "OS X" to "macOS". Apple renamed the operating system from "OS X" to "macOS" in 2016. The correct capitalization is "macOS". Please make this change everywhere else that it might appear as well.

Then, your instruction to run ".build.sh" has a typo. It should be "./build.sh".

Finally, it is untrue that the only way to get Uxn is to build from source. An alternative is to install it using MacPorts. When available, a binary provided by MacPorts will be used, and if a binary is not available, then MacPorts will build it from source. See https://ports.macports.org/port/uxn