I've seen that some people they have Visual Studio Code showing ≠ instead of a classic !=. Does anyone know how one can enable this option?
I've tried to search for an option to enable this, but I didn't encounter anything in the code editor's settings or the internet.
It's called a ligature. You need to get a font that supports the specific ligatures that you want to have.
To find out how to set it up for Visual Studio Code, see How do i setup font ligatures for Visual Studio Code?.
To find such fonts, try googling
programming fonts with ligatures. I won't list any because Stack Overflow is not for technology recommendations, and I don't want to seed bias or have to maintain a list when new ones become very popular.