Mastodon can theoretically run indefinitely on a free Heroku app. It should be noted this has limited testing and could have unpredictable results.
- Click the above button.
- Fill in the options requested.
- You can use a .herokuapp.com domain, which will be simple to set up, or you can use a custom domain. If you want a custom domain and HTTPS, you will need to upgrade to a paid plan (to use Heroku's SSL features), or set up CloudFlare who offer free "Flexible SSL" (note: CloudFlare have some undefined limits on WebSockets. So far, no one has reported hitting concurrent connection limits).
- You will want Amazon S3 for file storage. The only exception is for development purposes, where you may not care if files are not saved. Follow a guide online for creating a free Amazon S3 bucket and Access Key, then enter the details.
- If you want your Mastodon to be able to send emails, configure SMTP settings here (or later). Consider using Mailgun or similar, who offer free plans that should suit your interests.
- Deploy! The app should be set up, with a working web interface and database. You can change settings and manage versions from the Heroku dashboard.
You may need to use the heroku CLI application to run USERNAME=yourUsername rails mastodon:make_admin to make yourself an admin.