The whole idea of "disabling transcoding" is wrong.
The way UMS works is that it will only transcode when the renderer doesn't support the media as it is. This means that the only thing you achieve by disabling transcoding is that some media files won't play. This setting is meant for debugging only.
Each renderer has a renderer configuraton file. This file tells UMS what formats/codecs the renderer can play, and if this information is correct, UMS will never transcode a file that the renderer can play, so there is no need to disable transcoding. So, your real problem is probably that your renderer configuration(s) is/are wrong and doesn't actually reflect the capabilities of your renderer(s). This is what should be rectified to make things work properly.
The documentation for how to configure the renderer configuraton files is somewhat lacking, there is some documentation here:
https://github.com/UniversalMediaServer ... -support-1
You can also find a partial explanation in the default renderer configuration file itself (search for "supported" to get to the right section):
https://raw.githubusercontent.com/Unive ... derer.conf
In addition to these resources, there are countless threads on this forum on the topic, and you should be able to find pretty much any information you need on this forum with enough patience, but it can require significant reading and searching effort.
If you're lucky you can find configurations that other users have made and posted that fits your devices that either work fine, or that just requires minor adjustments.
To give an example, to "disable transcoding" for MKV's for a specific renderer, you just need to tell UMS that the renderer supports anything MKV. This is as simple as specifying
The problem is that I can pretty much guarantee that the renderer doesn't support all MKVs, since MKVs can contain a huge number of different codecs and combinations. So, you would very likely be "lying" to UMS if you said so, but if you only ever play MKVs with a limited set of codecs that the renderer does support, you would never experience a problem because of it. The idea is to try to limit the "supported" lines by specifying at least what audio and video codecs that are supported in a given container/format, which will make UMS send these supported MKVs without transcoding, but will still transcode a MKV with some rare/unusual audio or video codec. That way, the file with the we unusual codec would still play, although with transcoding.