Insert a video file from my hard drive (MP4/HEVC). The video is linked to, not embedded.
Add video subtitles in WebVTT format. Both the video and the subtitles play flawlessly in VLC Player.
Not so in PowerPoint: The video plays fine. But the subtitles do not even show up. I can spot a subtitle button on PowerPoint's video player bar. It is not visible when I do not add subtitles or remove them. So, I assume the subtitles have been added. But the button does nothing when I click it.
However, when I embed the video into PowerPoint, the same subtitles work just fine. But embedding is not an option for me. It takes too long, blows up the presentation file and reduces video quality. Most of all, the video is sped up so much that you cannot follow the dialogue and voices sound like Mickey Mouse.