How do you become a LM?

A lichess master?
is it when you reach a specific rating in lichess?

You simply do not become LM.

I believe they discontinued, this.

yes they did read the link i posted before

The LM title is given only to very strong players who do not have FIDE titles.
To be eligible for the LM title, you need to win three LM Norms. To do that, you have to win three Lichess Marathon tournaments where each one is 24 hours long.
Here is an example of such a player: @lance5500.