We learned that Google was trying to convince Samsung to kill Bixby in favor of the Assistant earlier this year — perhaps this is one of the results from those discussions.
The 2020 smart TVs that will receive support for the Assistant include Crystal UHD TVs, Frame and Serif TVs, Sero and Terrace TVs, and Samsung's 8K and 4K QLED sets.
Once the OTA update is installed, the Assistant can be enabled by going to Settings -> General -> Voice -> Voice Assistant.