- Ubuntu 18.04 will be EOL on April, 2022. So I make changes for installation document with Ubuntu 20.04 and Debian 11 support.
- Added PostgreSQL with latest version (PostgreSQL 14)
- [Yarn](https://yarnpkg.com/getting-started/install) is now a default package since Node.js 16.10, there's no need to install yarn classic.
- From Mastodon [3.5.0](https://github.com/mastodon/mastodon/releases/tag/v3.5.0), ruby 3.0.3 is recommend.
Tested in Ubuntu 20.04 and Debian 11, all works fine.