Before you mentioned it, I didn't realise that Google Takeout supported Dropbox, OneDrive and Box. Thanks!
Now, if only there was an API for me to automate the process (especially since I have multiple accounts).
I'd get an external HDD for this, instead of going from one cloud to another.
However this is not perfect either, because it means sharing my data with another big corporation. While majority of my files in GDrive are encrypted, some are not (e.g. emails). I am yet to find a good solution for myself.
I was thinking about spawning a machine in Digital Ocean, downloading data using Google Skicka [1] (which is awesome tool btw), encrypting with gpg and uploading to different cloud. I just don't know any unix command line tool that could upload to One Drive or Amazon. Any suggestions?
Another solution I am considering is machine in AWS that would download everything, encrypt and store it in Amazon Glacier [2]. I think I'll be eventually trying this once I learn more about Glacier.
EDIT: just did some googling and it seems that rclone [3] may meet my needs.
[1] https://github.com/google/skicka