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

It should not be linux exclusive though. I see that there are some firefox extensions that are targeted for VLC, so you could also try them.

I’m okay with it, except for the sliders. I can’t seem to differentiate 90%-100%

I use Linux and mpv to watch the videos. I use ‘Open with’ firefox extension and configure a shortcut to open links via mpv. That way, I can just right click in the video page >> Open with mpv. Rarely encounter problems this way.

Taiwan is not even in south east asia…