Make custom game launcher

Hello,
I create a custom launcher for my game.
I have “disabled” the old launcher (that of unity) and I’ll create the new.
I wish that when I launch the game, the launcher opens (I already try Dark Patcher)
Who would have a solution?

Best regards.
Ps: I am French and I use google translation, sorry

I have been interested in this myself but was not sure what to do.
I am still researching but have found some English tutorials:

https://www.youtube.com/watch?v=3i7sjJfFL9o,I,m not entirely sure how it works but I have been interested in this myself and here are some tutorials. (Except they are in english)
https://www.youtube.com/watch?v=3i7sjJfFL9o