Figured it out! I set VLC as the default, but that didn’t work. However, looking over the python for the skill, the skill assumes the files are mp3s by using the “stream.mp3” handler. I attempted to use the generic “stream” handler, but VLC wasn’t able to determine what format it was. For the time being I’m going to leave it with the “stream.flac” handler, since that’s 90% of my music. In the meantime, I’m going to look into the new stream api that emby has and push an update to the skill when I’ve got it figured out.
Thank you for helping me get to the bottom of this!