Install on your Desktom and Mobile Device the VLC Media Player Official
From the upper right of the page: Download for your browser
Download the folder windows read the instructions and install the app.
Now when you open a Hevc Movie online, you can hear the audio on a black screen.
Click the "Open In VLC" extension on your browser and the VLC media player show up on your Desktop.
Write your Nextcloud username and password and enjoy the movie.