I'm surprised by a lot of the suggestions (learn C?). I mean sure, everything is interesting, but what is the goal here.

There are many paths, I suspect you could use more exploration to know which ones appeal to you.

From my pov: - general backend people are a dime a dozen, deep front end expertise is harder to find. if you already have front end skills, adding deeper design/UX skills to that would take you to another level completely - on the backend, python unlocks a giant data / ML ecosystem, plus django