Shared videos does not fill screen correctly on mobile

Steps to reproduce

1. Share a video file (with high resolution, e.g. a full size mp4 from a modern android phone) as a link
2. Open the link in the web browser of a phone (or on a PC with a mobile selected in the device toolbar of the developer tools)
3. Start playing the video
4. Click the full screen button

Expected behaviour

Expected the video to fill the screen

Actual behaviour

This does not put the phone into a full screen mode, but rather increases the size of the video so that it is considerably larger than the size of the screen, so you can scroll around inside the view and always see only a subset of the full video.

Note that this does not happen when viewing videos when logged in to the web interface and choosing a video from my files. I assume this is because I have media viewer (v1.0.2) installed, and media viewer does not have this issue.

Server configuration

Operating system: docker container running on a Synology NAS

Web server: apache

Database: mariadb

PHP version: 7.3.11

ownCloud version: 10.4.0.4

Updated from an older ownCloud or fresh install: fresh

Where did you install ownCloud from: docker hub -> owncloud/server

Signing status (ownCloud 9.0 and above): no errors

The content of config/config.php: let me know if this is needed

List of activated apps: Default apps + 2-Factor Authentication

Are you using external storage, if yes which one: no

Are you using encryption: no

Are you using an external user-backend, if yes which one: no

Client configuration

Browser: Google Chrome (phone), Vivaldi (phone and PC), Firefox (PC)

Operating system: Android 10 and Ubuntu 18.04

Start by reproducing the shared-link video flow on a mobile browser, using the high-resolution MP4 steps in the issue. Compare it with viewing a video from the logged-in web interface and the media viewer; done means fullscreen video fits the mobile viewport without internal scrolling.