I recently read the following article:
https://blog.samuelmaddock.com/posts/google-widevine-blocked-my-browser/

and thought the two following links could help you:
https://castlabs.com/news/downstream-open-source-downloader-electron/
which shows that Castlabs implemented Widevine support in their custom Electron build

https://electronjs.org/docs/tutorial/testing-widevine-cdm