Hi Moon. Welcome to the forum.
You didn't say which version and architecture you're using. You can find out by running these commands:
$ version
$ uname -m
If you are using a recent version (12 or later) and x86_64 architecture, you can load (i.e., "install") the brave-browser extension, which supports video playback (from youtube and other sites) out of the box. This is how you load brave-browser:
$ tce-load -wi brave-browser