On Windows, if I just drag a srt file on to a playing video, the subtitles are displayed. On Linux, the dragging doesn't work. Now, mpv is my default player, so I just double click on the video file to play it. But I can't add subtitles. And I don't want to open my terminal everytime I play a video.
According to the MPV help page's subtitle section:
You need to put
sub-auto, and likely
sub-paths in your mpv.conf file (see link for examples). I'm not aware of any support for "drag and drop" subtitles addition in MPV.
I made a GUI so you can use it to make a MPV configuration file and play movies with subtitle using it (for GNU/Linux) :