elgavon Is there a way to open files in fullscreen by default?
Browsers don't allow to automatically "open fullscreen" without the user triggering it from some interaction (click).
The only workaround, would be to bind an event that takes the browser fullscreen on the first user click anywhere on the stage. Add the following to custom.js:
window.addEventListener('load', (e) => {
document.body.addEventListener('click', () => {
if(screenfull && screenfull.isEnabled) screenfull.request();
}, { once: true });
});