If I’m understanding correctly, you could sniff the communication between your Smart TV and the manufacturer using this method?
Possibly. But some manufacturers may not have the full set of roots, use a private authority, or do certificate pinning.
If the TV isn't older than a few years, if it's not checking CRLs, and if it hasn't yet patched itself.
As long as the smart TV still trusts eMudhra, then yeah. You'll want to super careful and prevent the TV from pulling updates that could revoke that trust.