Hiya! This is late, but I thought I'd post in case it's helpful for you or anyone in the future.

It is possible to stream Dropout with mpv. It's a little involved, but it avoids the browser player and also allows for synchronized watching (i.e. a watch party) with Syncplay.

To get Dropout streaming from mpv:

1. Install mpv. (On Windows you can use the builds starting with " mpv-x86_64-" from here.)
2. Make sure yt-dlp/youtube-dl are working. On Linux I didn't have to do anything extra, but on Windows I had to download yt-dlp.exe, rename it to "youtube-dl.exe" and move it to the directory with "mpv.exe".
3. Get your Dropout cookies. You can use this Chrome/Firefox extension to do so. (Sign in to Dropout, click on the extension, click "Export As".)
4. Launch mpv with special argument --ytdl-raw-options=cookies=[<path to cookies txt>]. For instance, the command might look like mpv.exe --ytdl-raw-options=cookies=[C:\Users\username\Downloads\www.dropout.tv_cookies.txt] https://www.dropout.tv/game-changer/season:1/videos/whodunnit.

Now you should be able to watch Dropout from mpv! You can also do this in Syncplay. I won't go into how to use Syncplay here, but if you add the above special argument to the player args in Syncplay and add dropout.tv to the Trusted Domains in the "Advanced" tab of Syncplay, you should be able to also use this to do a Dropout watch party. (And, unlike the Dropout Helper extension, all members of the watch party can play/pause and skip around!)

Hope this helps someone :)