uxn is a portable virtual machine, meaning that its programs are designed especially to be working on different consoles and devices. The same Uxn program can be used on a NintendoDS, on a desktop computer, in a browser, on tiny electronics, and modern electronics without having to do any changes to the code.
See the cheatsheet.
Follow the very thorough and very good Uxn tutorial by Compudanzas.
This guide will focus on getting you started with the Uxn emulator for desktop computers, but if you quickly want to try Uxn, you can load a rom directly in your browser by using the web version of Uxn.
The desktop emulator is built with SDL2, download SDL2 for your operating system.
sudo pacman -Sy sdl2 # Arch sudo apt install libsdl2-dev # Ubuntu
The next step is for you to download the uxn emulator:
git clone https://git.sr.ht/~rabbits/uxn cd uxn ./build.sh