ESP8266 / ESP32 - WIFI processors
These processors can be used for almost everything at a very low cost. They can be programmed from the Arduino IDE, Visual Studio Code + PlatformIO - has Wifi connectivity and is super easy to use!
If you have not tried these awesome processors yet - I recommend buying fx the NodeMcu boards with 4Mbyte of flash that works out of the box with Arduino IDE
The ESP32 has two cores, bluetooth peripheral and much more!