libebml 1.4.3 breaks MKVToolNix and VLC complains about codecs in mkv videos.
Mentioned in [Unstable Update] 2022-09-12 - Kernels, LibreOffice, KDE Gear, Wine, Cinnamon, Deepin, Qemu, Qt - #36 by clmbtti
Downgrading libebml to 1.4.2-2 restores functionality.
pamac install /var/cache/pacman/pkg/libebml-1.4.2-2-x86_64.pkg.tar.zst