A few days ago, I was trying to play a .mkv video that was giving me a hard time. VLC wasn't agreeing with it for some reason, so I ended up shifting my efforts to a slick media player I found on GitHub (IINA), but the video still wasn't wanting to open. After troubleshooting and looking trough some forums, I found a potential resolution I wanted take a shot at. I ended up changing the default application within the 'get info' window; selecting the 'change all..' option so that all .mkv files would open with IINA. This solved the issue I was having with the .mkv, which was great, but I'm starting to think this may not have been the best idea.
I was looking through ~/Library/ earlier today, and I noticed that several .dat files have appeared as filetype 'IINA document'.
Here's some examples: I don't know if this is even something to be concerned about, but it seemed strange to me. Is there any possible way to revert the change I made as if it never happened? I don't think there was any default application before I set one myself because I had to click 'other' and search through finder for an app that supported the original mkv.