Shirogane Ryu

My recomendations: Opensuse Leap 16, Mageia 9, Openmandriva Rock and if You want to try a Rolling release Opensuse Tumbleweed, Openmandriva ROME

All the disteos With KDE Plasma

Probably now all or almost all of the videos on my PC are in MKV format. It’s codecs of that files well it’s a story for another day

It’s not a self-hosted but I think that Image Toolbox (https://f-droid.org/packages/ru.tech.imageresizershrinker/) meets your requirements

I Used Gondolin for my PC but after reinstalling I didn’t put it back on and left the default

It’s propietary

To me, one of the best players for windows along with foobar2000

I used, but today I use Clementine (is still alive) and sometimes QMMP with some winamp skin

VLC It’s a good Music player if you only need to play music