I am recording some series with tvheadend and I am looking for a video editing software, simply for cutting the recording. Ibalways take few mninutes extra before and after the recording + I would like to take out the commercials.

So what I need is a simple editing tool that preferably supports matroska mkv format.
Then on the other hand, I like matroska a lot, but would I spare some disk space if I used something else? I think I do not have any of the features like different audio tracks or subs, so maybe I could go consider another final format...

I think it's hard to find an open-source video editor that doesn't support Matroska.

If you are looking for a full-fledged editor, check out kdenlive, Openshot, Cinelerra, and for simple editing, which seems to be your goal, avidemux.

Also google something like "linux matroska editor" and receive plenty of suggestions.

I haven't watched this Youtube playlist, but I've been meaning to.

Blender Video Editing (2014-2015)

Thx, I thought avidemux, for example, would be mostly about avis I did not realise matroska being so spread.
I'll have a look. I did not get anything meaningful out of google, just loads of software with price and you don't know which one is an established obe. Avidemux I have used...I hate starting using something and the next version of ubuntu leaves it out...

mkv is a container format (so is avi and mp4).
the actual file format seems to be of lesser importance - in the end it depens on the encoding & compression. and that is a real jungle.
it also depends on the skill of the encoder, but if you use tv streams one might expect that they're compressed with the best possible size/quality ratio...