Can cast videos but can't play them directly

[FitzWM]

Describe the bug
Hi, all. I'm not sure if this is even a bug or if I'm just misunderstanding what this tool is meant to do. I can cast videos from my media server perfectly with it, to both the TV connected to the server and my Linux desktop. It works flawlessly, it fixes all my problems with one tool, thank you. However, what I can't do is play a video file on my Linux desktop (using the Samba share connected to my Jellyfin server) and have the Shim "pick it up," so to speak. I want to be able to play a file using mpv, but with Plex tracking, without having to cast from my phone to my desktop every time.

Is that possible? This seriously may just be me not getting how this thing works. In my head, though, it makes sense that I should be able to tell Shim, "OK, you know that thing you do when I cast a video to you? Do that with this file here."

To Reproduce
Steps to reproduce the behavior:

1. Cast video from phone. Video opens MPV Shim GUI and plays perfectly fine.
2. Open video from Dolphin, terminal, etc. Video opens in normal MPV with nothing happening in the Shim console.
3. Try to open video with Jellyfin MPV Shim, rather than MPV. A new Shim instance is spawned, but nothing else happens.

Expected behavior
I open a video file on my Linux desktop, using my Jellyfin server's file share, and it opens in the MPV Shim client, connected to the Jellyfin server and tracking properly.

Screenshots
N/A

Desktop (please complete the following information):

• OS: Linux (Ubuntu 22.04 LTS Jellyfin server, Arch Linux desktop)
• Version: 2.6.0

Error Messages
No errors that I can see. Just nothing happens.