@aamilo
The Roku 4640 is still supported. It has the same processor and hardware as other Roku models that are unaffected by the update. https://developer.roku.com/docs/specs/hardware.md
I would initiate another support chat, inform Roku support what this other clown support tech told you and request some sort of discount on a new Roku device if the official response is going to be "too bad, we broke it, so buy another one."
While you device is older/old, and you would likely benefit from a newer device, this response from Roku is unacceptable. (and likely just an uninformed customer representative assigned to online chat duty).
It is entirely possible that you may just have a device failure, but if Roku is informing you that their update was the cause of the failure, they should be able to revert it back to the last stable version while they investigate.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102