If you are using a bash shell on Linux, you should consider creating a script to set the main environment variables and launch Katana for you.
KtoA 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.
KtoA includes two components from Arnold-USD to allow using Arnold directly in the Hydra Viewport.
KtoA includes a custom build of Foundry's Katana USD Plugins, which replaces Katana's one when using the launch scripts. There is also a set of plugins for UsdIn, named KatanaUsdArnold, included in the installation. These allow importing Arnold specific information, like shaders, using UsdIn.