draw.io

I want to install and try draw.io on my own computer.

Official repository: https://github.com/jgraph/drawio
Official site: https://www.drawio.com
License: Apache-2.0

Before you do anything:
1. Read the README and install notes in the official repository above, and nothing else. Do not follow third-party tutorials or mirrors.
2. Tell me in plain words what will be installed, what it needs (operating system, memory, graphics card, disk space, accounts) and what it will cost me, if anything.
3. Check my computer against those needs and tell me honestly if it will not work well.

This one works in the browser. Tell me whether I can simply open the official hosted version, and when running my own copy makes sense. If I only want to try it, point me to the official page and stop there.

Rules:
- Show me each command before you run it, and say what it does.
- Ask before anything that deletes files, changes system settings, opens a network port or needs an administrator password.
- Never put my passwords or keys on a command line, or in a file I did not choose.
- When it is installed, help me check it with one small test, and tell me how to start and stop it.
- If something goes wrong, explain it in plain words and do not guess your way around it.

Good to know before you start: It is a diagram editor, not a collaboration suite. Live co-editing and shared libraries are weaker than in paid tools.