I never found YT to be a reliable source of ps3 information, I much prefer tutorials or guides written by people who know what they are talking about.
Anyway what you are really after is a tutorials about the old official way tout prepare your hdd for Linux, in the other words tutorials that are 10+ years old..
The attached pdf tells you what to do, only the part called "PS3 Preparation" (on pdf page 4 but it is really the guide's page 3) is relevant.
View attachment 35327