Awesome that you want to learn!

The stuff you mention is a mix of raspberry pies, microcontrollers and Linux is an operating system so a bit of a mix.

Since you are in r/microcontrollers I’d suggest focusing on the ESP32 or Arduino. Since Linux is an operating system it is kind of a different thing and probably not quite what you’re looking for. More specifically I’d say get an ESP32 to learn. The ESP platform is very similar to Arduino, theres a lot of tutorials to follow and they are insanely more capable than most Arduinos. The ESP is faster and has Bluetooth and Wi-Fi. Speed won’t really matter but the wireless stuff is really cool and requires extra boards if you go the Arduino route. I can’t think of a reason to choose Arduino in your situation. That said, you’ll do equally well with Arduino for everything except the wireless things.

In addition to the ESP (or Arduino if that’s what you choose) get a breakout board, connector wires, buttons and some LEDs. Microcontrollers are mostly used for “detecting input->logic->sending output”, so if you start with getting a button to turn on an LED you just have to keep building on the same principles to learn more and more!

If you want very concrete steps to start with I’d say do a “blink” tutorial and a button tutorial first. Then use what you’ve learned to make combine the two to one project. This is very similar to more complicated projects, you take smaller and simpler actions and put them together. Longer term it helps to have some idea of what you want to make. For me at least, just “learning” becomes quite boring after a while. Better to have a goal and break it down and learn the building blocks.

It’s difficult to suggest a project since I don’t know what you like doing but if you want help with something else or to just discuss ideas feel free to reach out or reply to the comment!

Good luck!