Basically my box is a h96 pro + (amlogic s912) and I'm trying to run prime video / netflix, but it is not possible since it is only possible to extract widevine in the arm-32bits version. I searched here on the forum and found nothing about it, so I ask for help.

No, we were thinking about that, but never got there to start working on that. For a few people that maintain this, its low priority.

I don't have specific experience with widevine but debian-derived distributions including armbian are capable of hosting multiple ABIs. 

Your s912 is aarm64 but is backward compatible with armhf. Your 32-bit arm binary is armhf. Similar to how an amd64 system is backward compatible with an i386 system. 

 

You start with dpkg --add-architecture armhf

 

then apt-get update

 

Then you install 32-bit versions of everything you need for your 32-bit netflix, etc with "apt-get install foo:armhf" and so on. 

 

I've only done this on a small scale, but if you get lucky and everything you need is in the distribution, it's pretty painless.  the "ldd" command will tell you what libraries a dynamically linked binary needs to have around. 

 

more info here: https://wiki.debian.org/Multiarch/HOWTO

If you can not play the video. Then there is with your browser’s widevine plugin. This happens when the plugin does not updates with the latest version.

How to fix Widevine Content Decryption Module update error

Update your plugin.

Enable Widevine Content Decryption Module.

Reinstall the Widevine Content Decryption Module.

Try to give full permission to Widevine Content Decryption Module.

I found this amazing way to fix Widevine Content Decryption Module.

you can read full guide from here https://www.techbian.com/widevine-content-decryption-module-update-error/