Do there exist clients that can seamlessly read, cross-post, and reply to multiple social media networks? Something like an RSS feed reader with a unified timel

Do there exist clients that can seamlessly read, cross-post, and reply to multiple social media networks? Something like an RSS feed reader with a unified timeline of posts from any number of networks. Do X and Meta’s terms of service even allow third-party clients there days? I follow some accounts on both Twitter and Mastodon (as a backup in case the account leaves Twitter or is blocked) so such a client would need some smarts to de-duplicate posts that other people are cross-posting.