[Stephen]

I have the Tab S6.

For watching videos I use MX player from the play store. There is a free and a paid for version(MX player Pro). It scans the device and will list all playable video files. Plays every file I've chucked at it.

Or if it's just stored videos open the gallery app and if the videos show there, they will play when you click them.

If that's what you are looking for?