from the youtuber DroneBot Workshop (~300K subscribers).
I found this just-uploaded tutorial / primer for PlatformIO quite good. It shows installation, library management, the serial monitor, the library manager, differences between
.cpp files, a project on 3 different boards (Uno, ESP32, SeedStudio Xiaomi) and a more complicated servo motor project. A beginner’s initiation to PlatformIO for Arduino IDE users, so to say.
Also has an accompanying article: https://dronebotworkshop.com/platformio/
(@ivankravets: Content should also be added to https://docs.platformio.org/en/latest/tutorials/index.html#community-video-tutorials ?)