Apple TV app on Samsung TV

It should be pre-installed or else available from the Samsung App Store, for their smart TVs from 2017 or later, in most counties where the Apple TV subscription service is available. Samsung may differentiate app availability per country. What is your country?

Access to the Samsung App Store would require being signed in with a Samsung account.

Use apps on your Samsung smart TV and projector - Samsung

Apple TV app for Samsung smart TV and projector - Samsung

Get the Apple TV app on your smart TV or streaming device - Apple Support

Watch on these smart TVs and third party streaming devices - Apple Support

Apple TV was not available in that region, and just recently became accessible to users who subscribe to iCloud Plus. There may be an incoming roll out for the app, but this is just a user forum so no one would be able to answer any specifics.

Best to contact Apple support so they can assist.

Contact Apple Support - Apple Support (CA)

I'm already signed to Samsung account on tv. Country is Serbia. I've contacted Samsung support and they said that something should be coordinated on the apple side and that it depends on apple, but that the application will certainly be available soon.

Country: Serbia. The TV was purchased in Serbia. I am signed in with my Samsung account and have access to the Samsung App Store. Other apps (such as Rakuten TV) are available, but Apple TV does not appear in the App Store search at all. My TV model is Samsung QE50Q67CAUXXH (2023).