In this tutorial, you will install the latest version of Mastodon, which is 4.0.2 at the time of this writing. You will configure the official Mastodon install repository, and set up the environment to install all other dependencies. Using the interactive setup, you will set up your custom Mastodon instance for storage, email, assets, and your administrator account. Finally, you’ll secure your instance with SSL/TLS certificates through Let’s Encrypt.

Source: How To Install Mastodon on Ubuntu 20.04 | DigitalOcean