If you're using a Nvidia 10XX series Pascal card on a Linux distro (or even an older 900 series GPU and newer), you should be using the proprietary Nvidia driver and not the open-source Nouveau driver,
especially if you're intending to watch video. Nouveau
barely supports the 10 series of GPUs with only the bare minimum working so it's not surprising MC25 can't correctly playback videos without it. Open-source Nvidia support on Linux is notoriously bad, since Nvidia doesn't exactly support the community, unlike AMD. Nouveau developers basically have to reverse engineer the support for newer GPUs, which only can go so far unless Nvidia releases signed firmware to get basic support working in the first place (which as far as I know hasn't happened for the 20XX series of GPUs yet). And even today, there's still no reclocking support for 900 series GPUs which are, what, nearly 5 years old now?
Yes, I know other media player apps will play the video files, but MC needs hardware acceleration to playback video, which is pretty much lacking with Nouveau. So there is indeed a point in changing video drivers, since Nouveau is pretty sub-par for newer Nvidia GPUs.
Some info here:
https://linuxconfig.org/how-to-install-nvidia-driver-on-debian-10-buster-linuxAnd more here:
https://www.reddit.com/r/debian/comments/cc7n6v/how_to_install_nvidia_drivers_in_debian_10/I'd do the first part, enable the non-free repo (you can do this in the Software & Updates app, just check the box for non-free) then use nvidia-detect and follow its recommendation (likely installing nvidia-driver).