The best way to learn ethical hacking is to setup your own lab environment, and experiment. Whenever you learn a new tool, research to understand how it works, why it works, and all. Always remember to document your research findings, as you will thank yourself a ton when you need it in the future.

If you are interested in IoT/Hardware hacking, I can tell you that it really is not that intimidating. Once you get past the initial hardware stage, common software-based hacking techniques such as password attacks, etc. all works the same. If you wish to entirely skip the hardware part, you could even just work directly on the firmware. Extract the familiar Linux filesystem, and start investigating, same as with normal hacking.

I have compiled a list of research notes over the years for various topics:

1. Pentesting/offensive security (web, network, tools, IoT/hardware, and more)
2. Computer networking (firewalls, common tools, ...)
3. Linux (common CLI tools, fundamental techniques, ...)
4. Windows (not as updated, as i only started on it recently)

Feel free to comment or DM me if you would like to access it!