"Widevine Dump":Leaked Code Downloads HD Video from Disney+, Amazon, and Netflix

Am I correct that homomorphic encryption will solve the DRM problem, in the sense that it will be mathematically proven (in the cryptographic sense) to be impossible to bypass?

Of course, you'll still be able to cam-record the actual output, or steal the image from the TFT/OLED electronics, but no easy bypass.

You are wrong. An encryption, any encryption, needs a key for decryption process. If the client is given that key then it can decrypt and rip the content. If the client is not given the key then how will they legally watch it since they paid for the content anyway?

As a rule of thumb, anything that was made by humans can be unmade by humans. All you can do is make the pirate life harder, but never impossible.

The issue is that the image will always exist in a decrypted state if you're presenting it to the user. You can push that decoder further and further down the pipeline, but there's always a clean framebuffer to rip, no matter how you frame it. Yes, they could make it harder, but I could also design an Arduino that dumps the serial output of your decoder before it reaches the display controller. It would take some borderline space-age technology to design an IC resistant to that sort of vuln.