Shirogane Ryu

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

I like more Org Mode but I know that Markdown now is more universal. But… The best of both formatos is that I can use any plain text editor for read and editing it

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