How to set up an all open-source IT infrastructure from scratch

https://www.networkworld.com/article/3217713/open-source-tools/how-to-set-up-an-all-open-source-it-infrastructure-from-scratch.html

Hypothetical: You need to set up the IT infrastructure (email, file sharing, etc.) for a new company. No restrictions. No legacy application support necessary. How would you do it? What would that ideal IT infrastructure look like?

This presents writer’s ideal setup based on open source software.