On Linux, if you are using a bash shell, you should consider creating a script to set the main environment variables and launch Katana for you.
KtoA Katana to Arnold ships with multiple USD plugins, a Render Delegate, a Node Registry Plugin, a custom build of Foundry's KatanaUsdPlugins, and plugins for UsdIn. These plugins can be activated by either using the launch scripts or manually setting the environment variables listed below.
Katana to Arnold includes two components from Arnold-USD to allow using Arnold directly in the Hydra Viewport.
There are a few more environment variables of interest: