Firefox _does_ have support for running this daemon-like-thing for you using Native messaging[0] though.
youtube-dl-firefox-addon[1] seems to employ this, so perhaps give that one a try?
[0] https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...
I've been using a combination of firefox/chrome with youtube-dl/mpv+youtube-dl for a while
This comes very handy for playing high quality youtube videos on low end machines or downloading audio+/-video directly from youtube.
On the pre-webextension era of firefox/chrome , "open with" addon was the perfect fit.
Now, a special native messaging app needs to be installed to launch mpv/youtube-dl
"Open with" addon solved this by a python script (that obviously required installing python, and few other steps)
I decided to create a new tool to make this step easier and faster on windows: owclauncher[1]
Basically a lightweight native messaging host for "open with" addon: it is not running on the background, and only started (and immediatly terminated) by the browser when passing a command to any other program
You can check and compile the source code or the .bat windows installer/uninstaller
Thanks!