External subtitles on Apple TV

I know that when using cloud storage resources, you can add subtitles by placing the subtitle file and video file together. However, when I use third-party media servers like Emby and want to use external subtitles, how do I add external subtitles?
Is it possible to add external subtitle iCloud sync to Apple TV?
Thx. :smiling_face_with_three_hearts:

https://emby.media/support/articles/Subtitles.html

Can’t I use external subtitles for third-party Emby?