Pause media with spacebar
Single click / double click on the video frame seems to have no effect for playback. Spacebar also has no effect. The only way to pause a video is to hit the stop button which seems to have been misplaced in the top of the screen, while traditionally it is always next to the play/FF/etc buttons.
https://www.reddit.com/r/linux/comments/dzh42b/girens_a_gtk_plex_media_player_client_just/f8prg2b/