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KoenI always use
youtube-dl, maybe that will work for you?
I use youtube-dl as well from the command line or youtube-dl-gui which is the same thing but with a graphical user interface.
The source code of the youtube-dl software is open to see / or even to alter.
So,it seems to be the safest option.
Maybe if you are using a mobile phone,you would need some of those other options but,youtube-dl works with all of the major desktop operating systems.