Search for widevine decrypt. You’ll find code and forums where at least some L3 (software) keys are publicly shared. For high resolution on some platforms, you need L1 keys, but as far as I understand the decryption process basically stays the same once you have a working key.

Random article: https://www.ismailzai.com/blog/picking-the-widevine-locks

Claimed to be L1 key leaks (probably all blacklisted by now): https://github.com/Mavrick102/WIDEVINE-CDM-L1-Giveaway