How to completelly remove Widevine from Brave (Ubuntu)?

Thanks for reaching out to us. So as it stands we don’t have a way to disable/uninstall Widevine CDM in settings – there is an open issue to add this feature which I’ve added a +1 to on your behalf:

However, on Linux, you may want to try checking and removing the following:

rm -rf ~/.config/BraveSoftware/Brave-Browser/WidevineCdm

Please be sure you do not remove the entire directory.