I have troubles understanding what's the value added by Yattee if it's only a "front end", while piped already claims it's a front end for YT. Can you help me get a clearer understanding ? I'm interested in ditching YT in favor of a privacy friendly / ad-free alternative.
Yattee aims to fit more in line as a native Apple subscription organizer and player application suite, with native window controls and tighter integrations, but it's mostly up to you to decide how'd you like your setup to be.
Ideally, you could self host only the Piped framework and connect this to Yattee without hosting the WebUI frontend, but without the latter, you cannot create a user for yourself to store subscriptions, and using the provided AIO Docker Images is overkill for self hosting as you are required to purchase and point to DNS records for this system (mostly to the benefit of publically hosting an instance of Piped).
Invidious is more suited for this regard, but has issues with parsing some videos and their metadata (usually new uploads for a week, Vevo Music Videos etc.)
Yattee is a good front end app for both piped and invidious for Apple TV (and iOS and macOS but I prefer the browser on those platforms)