How do I know that my smart tv support Apple TV

Depends on what you mean by "support Apple TV".

Do you want to know if it can support the Apple TV streaming device?

or

Do you want to know if it can support the Apple TV App directly on the TV without any other device?

The Apple TV device just needs a free HDMI port.

To find out if your TV supports the new Apple TV app directly on the TV however, see here: Apple TV app - Devices - Apple

If it has an open HDMI port, use the output of your Apple TV to your TVs input and you’re good to go.

Simple as that. Open HDMI is all you need and is you are using ARC through a switcher via an amplifier, you need one there too. Not sure what else could block anything from being conpatible.

To make it more clear, your question is a kin to asking if “my TV is compatible with Xbox or my BLU-RAY player”.

So yes. It is as long as you have a port.