In response to Joe Biden and the White House enabling ActivityPub federation via Threads, a number of people asked: "Why didn't the White House just self-host their own Mastodon server?"
Here's some very basic musings on what it would take for that to happen. and what some of the hurdles are. Don't consider it a definitive answer, but a jumping-off point.
On that point i note that you can, if you have a paid account use Fedica to post on Mastodon within Hootsuite - but surely they are considering native supoort? https://fedica.com/blog/how-to-schedule-mastodon-posts-in-hootsuite/