It appears you are trying to use your iMac as a hotspot. While valiant and a nice idea, let's try this with a WIFI router connection.
Bob
Trying to connect Smart TV to built in Airport on iMac. Problem is with Airport saying it has a self-addressed ip address and won't connect to internet. I have exhausted myself googling for solutions... My iMac is connected to a router with an ethernet cable.

Chowhound
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