If you see an error that says
Due to technical limitations, Netflix will no longer be available on this device after December 1st, 2019. Please visit netflix.com/compatibledevices for a list of available devices.
It means that, due to technical limitations, your device will no longer be able to stream Netflix after the specified date.
This message will appear multiple times before the specified date as a reminder. To continue streaming, you'll need to switch to a compatible device prior to that date. To see a list of compatible devices, visit netflix.com/compatibledevices.