I like using Retroarch to play old 4:3 content with CRT shaders to mimic how this content looked originally. Currently, I have not found a way to accomplish this with muOS.
Using AnotherStockMix on the TrimUI Brick, the media player allows menu access to Retroarch options. From there, it’s very simple to pick a shader or two, then save them as a preset for the FFMPEG core or override. Afterwards, all media content opened has the preferred shader applied automatically.
Using Surwish OS on the Miyoo Flip, I open up the Retroarch app to play the content/load the core, then apply the shader, again saving as a preset for the FFMPEG core (playing media through the default Surwish OS media player gives no menu access to Retroarch, which is why playing the media through the Retroarch app is necessary).
I really enjoy muOS, but unfortunately I have not found a way to apply shaders to video (and maybe it already is possible, but I can’t figure out how). If possible, the direct access to Retroarch from played media would be the best option, as it involves less steps than accessing the Retroarch app like I have to with my Miyoo Flip/Surwish.