Would love to know the answer to this question. Still not able to get it on my Q80T despite mually updating to the latest software. Its one of the main reasons I bought the TV and if I can't get ot I want to return my TV. Did you get sorted?
I'm having the same issue with a TV that I bought last week. It was sold as "SAMSUNG The Frame QE43LS03TAUXXU 43" Smart 4K Ultra HD HDR QLED TV with Bixby, Alexa & Google Assistant". I followed all the update/reboot instrucctions from the US Support website and got nowhere. Called the UK/Ireland support and the attendant told me "We do not have Google Assistant in-built in any of our TVs". She did not seem to be aware that this is available in the US (and now seemingly in the UK & Canada as of last last year). Very frustrating as this is also one of the key reasons I bought this TV.
Don't waste your time with Samsung support. I've been waiting for a product support specialist to contact me for 5 months. Reached out on Twitter, no help. Can't get a straight answer from anyone. I bought my TV in Harvey Norman and have been plaguing them every since I've bought it. They've acknowledged I should have it but have just told me the same old instructions to update etc. I'm going to have to report them to the CPCC at this stage.