I've also given gtk-youtube-viewer a spin but it doesn't do "new videos of your subscriptions" (though it's command=line equivalent 'youtube-viewer -SV' does). Any recommendations out there for similar YouTube frontends?

Also, at least in the UK, youtube-dl can access BBC iPlayer content without the login required on the web.

  mpv() {
    if [ $# -eq 0 ]; then
      env mpv "$(xsel -b)"
    else
      env mpv "$@"
    fi
  }

  $ mpv "&& rm -rf /"
  Playing: && rm -rf /
  [file] Cannot open file '&& rm -rf /': No such file or directory
  Failed to open && rm -rf /.

I'm a heavy youtube-dl user and command line addicted myself, but cannot imagine an advantage in using youtube-dl for live-playing a video, when using the browser seems to give the same experience.

Much more involved than a single click that never even has to open a new tab.

Using key presses to navigate through and control media like this feels vaguely reminiscent of the first few times you really grok the power of editing a huge file with some well articulated vim or emacs commands. Also mpv seems less resource intensive whilst the browser has a lot of tabs open.

How did you do that? I would really like to have that setup also.

https://addons.mozilla.org/en-US/firefox/addon/open-with/

mpv can easily be configured to open full screen on a specific screen.

I've audited the script for the extension I posted and it looks good, I've posted mine here: https://www.pastery.net/dyeamx/

After reading the documentation for mpv I found the options --screen=<default|0-32> and --fs-screen=<all|current|0-32> these are used for selecting a specific screen.

https://www.pastery.net/vurryk/