If you have a file called 'file.mp4', then putting '[sound:file.mp4]' in a field will show the video on all platforms. The computer version does not support embedding videos - they are played with an external media player.
I was successful in imbedding videos (imbedded, not needing an external viewer) with the computer version (MacOS) using Anki 2.0, until MacOS Catalina. I have never got the imbedding to work with Anki 2.1 (MacOS Catalina or earlier versions).
Anki has only ever officially supported sound tags. You may have been able to get certain videos to embed in the past, but that was a side effect of the toolkit we were using rather than something Anki was explicitly supporting.
Ok, thanks for the information. I think I can continue my routine (successfully view cards with imbedded videos and with the dropping of syncing support for Anki 2.0) if I use the computer version 2.1 for maintaining the database (adding and revising cards) but use my iOS device for actually reviewing and learning.
Right -- thanks. I like the way they appear (and sound) on my iPad although Anki 2.0 with MacOS pre-Catalina was fine, too, and had the advantage that I could do everything in one place. This split, though, is not a huge inconvenience.