The two big obvious ones are Rails and Django. If you want a less common, more mind bending, more cutting edge experience, try Phoenix.
Rails and/or Django. Check what's more popular in your area.
React. A lot of demand right now, great for freelancing.
Not a real answer, but more like some food for thought:
https://kukuruku.co/post/do-not-learn-frameworks-learn-the-a...