TransDEM Forum

Is there a way to deactivate PBR texturing (and using standard textures instead) before exporting a TransDEM route to a pre-TZ2019 version of trainz?

That's controlled by Trainz Content Manager and which TransDEM texture set version(s) you have installed. TransDEM sets the texture KUID without a version number, and Trainz Content Manager will automatically apply the highest version installed.