java.lang.UnsatisfiedLinkError: Can't load library (libawt_xawt.so)

What it looks like in the log

java.lang.UnsatisfiedLinkError: Can't load library

How to fix it

1. Install the full (non-headless) OpenJDK package for your Linux distribution so GUI libraries are included: on Fedora run 'sudo dnf install java-17-openjdk' (or java-21-openjdk for newer Minecraft versions); on Ubuntu/Debian run 'sudo apt install openjdk-17-jre'; on Arch run 'sudo pacman -S jre-openjdk'.
2. If you are using a Wayland desktop session, make sure Xwayland and standard X11 client libraries (such as libXext, libXrender, and libXtst) are installed so Java AWT windows can render.
3. Check whether the JAR file you ran is an actual installer or a regular mod file: if it is a standard mod JAR (such as 'iris-mc1.20.2-1.6.10.jar' rather than the standalone Iris Installer), do not run it with 'java -jar'—move it into your '.minecraft/mods' folder alongside Fabric Loader and Sodium instead.

Check your own log