freerouting is a Java application.

freerouting requires java version > 16

Note: it has to be version 17 of Java for the KiCad plugin to work correctly.

sudo apt install openjdk-17-jre

installs version 17

To verify that you are running the correct version, run

java -version

You can find out whether you have multiple Java versions installed on your system by running

update-alternatives --config java

If you have multiple Java versions installed on your system, you can set the default Java version by running

sudo update-alternatives --config java

In the KiCad main window,
go to Tools -> Plugin and Content Manager.

freerouting_plugin

Note: Adding teardrops to the tracks seems to crash freerouting.

downloading the zip file from the installer link
https://github.com/freerouting/freerouting/releases
works
go to bin and run freerouting

freerouting