do i have to have an apple device to join apple tv

If you refer to Apple TV+ and the Apple TV app, then know that those are now also available for some third party devices. Thus Apple devices are not strictly needed. An Apple ID account is needed, though.

Get Apple TV+ - Apple Support

Devices you can use with the Apple TV app and Apple TV+ - Apple Support

Third party Apple TV app-supported devices - Apple Support

Apple ID - Official Apple Support

Hello,

Owning an Apple TV does not require having another Apple device. You can complete Apple TV’s setup directly on Apple TV.

Set up your Apple TV - Apple Support