Same here. I do not know if it helps... I have found a recipe for getting libwidevinecdm for vivaldi from
External Content
gist.github.com
Content embedded from external sources will not be displayed without your consent.
Through the activation of external content, you agree that personal data may be transferred to third party platforms. We have provided more information on this in our privacy policy.
Feeding the URL to "Input stream helper" did not help, neither feeding it with downloaded .bin.zip or .bin file.
I have managed on my Linux box to extract libwidevinecdm.so file from the image.
Now I wonder if what would be the place to put it?