I'm starting to use Blender 2.8 and have a question : Is there something like UV Squares that I could use to make my UV islands straight? Thank you !
Why not use UV Squares? I got it working in 2.8.
Install both 2.79 & 2.8 version of Blender. Current UV Square which is provided in Github working fine with 2.79 version. Save your UV layout with your model and then open the .blend file in 2.8. This is the only work around at this moment.