I used this instruction to setup ionic build environment: https://docs.moodle.org/dev/Setting_up_your_development_environment_for_Moodle_Mobile_2
I used ionic to build locally.
In Android & Chrome, Files don't open, e.g. PDF or PowerPoints.
In Android it doesn't show any message, just file doesn't open, but user can open file in browser.
In chrome it says: Failed to load PDF document.