Seems like Piped and Invidious are both on their last legs. Public instances on both services are pretty iffy, they go down fairly often now. Freetube works well on desktop but no real way to sync subscriptions and watch history to a phone. Self-hosting Piped/Invidious might be the solution but I don’t know if it’s worth the upkeep when YouTube is actively fighting against it.
It’s automatically handled by https://github.com/tubearchivist/tubearchivist-jf.
It works by identifying the videos downloaded by Tube Archivist and sending the info to Jellyfin. It hooks into the API of Jellyfin and adds the metadata.