@khteh To answer your questions:

Is there python equivalent of this page https://discord.com/developers/docs/quick-start/getting-started?

Yes, there is. discord.py's introduction page (and the quickstart) covers the basics and an introduction, but it is not an in-depth guide. In addition, it is strongly recommended to read the examples found in the repository, as they will cover other parts not covered by the introduction.

If you have any questions or need to seek clarification, then it is recommended to post your question in the discussion section as done before.

Do I need a Flask/Quart and FastAPI/Hypercorn server to run a custom bot?

No, discord.py effectively runs the bot by itself. Thus, there is no need for any WSGI/ASGI framework and servers to use.

How do run a custom bot locally and test it on Discord. For example, using ngrok?

The easiest way is to see the quickstart page. This document does and should explain a quick rundown, which would clarify the question.

Does it support /command?

Yes, slash commands are supported. It is recommended to view at the example for slash commands. Although not an official resource, AbstractUmbra has an more in-depth explanation and examples, which most have found extremely helpful.