Meta's Threads is the fastest rising Twitter alternative, but lacks some of Twitter's features, while it's still under development. For example, you can't yet save draft threads, search for trending topics, or use hashtags to find related content.
Mastodon is the best decentralized Twitter alternative which, like Threads will soon be, is connected to the fediverse for distributed sharing, and has open-source ownership.
There are a number of other strong alternative platforms you might consider to reach more niche communities, or prioritise different kinds of content, as we've outlined in this article.