How to watch a youtube video without all the added white space

[Telmesomething]

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When somebody sends me link to any youtube video on Signal or another app it opens full screen on my Android 13 phone, but when I open a URL myself two thirds of the screen is filled with a white background which contains animations and various buttons and the actual video I want to watch appears at the top. So my question is what do I have to do to remove all that crap below the video? Here's a pix of it:

Additional information

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[Telmesomething]

Never mind... I just noticed it'll display fullscreen if the phone is physically turned sideways into landscape mode.

Also, I found a review of it on ghacks.net where it mentions that the phone can be set to start fullscreen, but it didn't work on my phone when I tried it.