Some links to Raspberry Pi-related resources:
IOTstackIOTStack [Script for installing Docker images onto Rpi 3 and Rpi 4]
PicoRaspberry Pi Foundation just released their new processor chip for the IOT marked, the RP2040. Current price around USD 4,00.
They are also offering the chip on a small 40+3 pin developer-board with USB-connector (Micro) for simple program transfer. Using the VSYS power input the board may be powered with 1.8-5.5Volt using the onboard Buck/Boost converter!
They also offer a SDK-package and a lot of manuals on both HW and SW.
In a short while several producers will be offering boards with additional HW (and firmware??) (primarily WiFi; I guess) in order to compete with existing boards using the Espressif ESP8266 and ESP32.
Links to documentation: