Step 1: Understand the rebranding.
Twitter underwent a rebranding after being acquired by Elon Musk.
Step 2: Identify the new name.
The platform was officially renamed to ``X''.
Step 3: Analyze other options.
Threads is a different social media platform by Meta.
Mastodon is a decentralized social network.
Telegram is a messaging application.
Step 4: Conclusion.
Therefore, the social media platform formerly known as Twitter is now called X.