Full disclosure, I haven’t yet made the switch away from the official client yet, but you could give Wholphin a try for android TVs. It lists customization as a selling point.
GitHubGitHub - damontecres/Wholphin: An OSS Android TV client for JellyfinAn OSS Android TV client for Jellyfin. Contribute to damontecres/Wholphin development by creating an account on GitHub.