For the UV Squares:https://github.com/Radivarig/UvSquares
For the packer: https://www.uv-packer.com/blender/
UV Squares is free on GitHub (.py)
https://github.com/Radivarig/UvSquares/blob/master/uv_squares.py
but $20 (.zip) on Blender Market
https://www.blendermarket.com/products/uv-squares
