You could install and run an instance of Mastodon. That's (apparently) easy to do, under your control, and has most of the features that you could want. You c

You could install and run an instance of Mastodon. That's (apparently) easy to do, under your control, and has most of the features that you could want. You can use it for DMs and for broadcast, and if you deliberately don't federate then it will remain private.