Linux variation is simply because it was named after a Finnish person but became mainstream in parts of the world that pronounce those letters differently.

There are recordings from the early days where Linus clearly says “I say Linux as LEE-nuhks”. That is consistent with how you say his name in Finland. So, some people seize on that.

More recently, Linus has said that his name is pronounced differently in different languages but that “Linux is always lin-nuhks”.

Based on that, I thinks his latter guidance is correct. It is also basically the way most people in North America say it by default in my experience. This makes sense as Linus now lives in the US.

Ubuntu is an actual African ( Zulu ) word. It has a proper pronunciation.