Do you have some examples, showcase or demo somewhere to see the actual final result? Thanks

Sure! The README links [1] to several installations used by large Open Source projects and companies. Some prominent examples:

- https://fastapi.tiangolo.com/

- https://crystal-lang.org/reference/

- https://docs.pi-hole.net/

- https://docs.openfaas.com/

- https://mozillafoundation.github.io/engineering-handbook/

- https://microsoft.github.io/code-with-engineering-playbook/

[1]: https://github.com/squidfunk/mkdocs-material#trusted-by-

Is this g3doc?

No, it's just a theme for MkDocs [1], a static site generator that has no affiliation with Google. Material for MkDocs only borrows the Material Design philosophy from Google.

[1]: https://www.mkdocs.org/