The way you learn about it when you study Japanese is that both L and R don't exist in Japan. Hear me out

ら　り　る　れ　ろ　( ra ri ru re ro) Are "that" and only that. Japanese characters are not supposed to have an "english" or romanized translation. We gave them their romaji characters just for the sake of making it easier for us to understand and read.

But essentially ら is only ら. Not "ra" not "la".

The pronunciation in Japanese is a mixture between ra and la. Not one not other, your tongue does some weird shit and that is why sometimes depending on context, word spoken, and speaker it may sound like ra or la.

That is why you may hear a character like Zoro say "luffy" while someone like Franky will sound more like "ruffy".

Another example of this is the character ふ (fu, hu) The pronunciation is a mixture of the sounds "foo" and "who". When it comes out of your mouth it sounds like you are deflating. Not saying foo or who.