Review on 🔌 Smallest Arduino Microcontroller Seeeduino XIAO - SAMD21 Based, Enriched Interfaces, Fully Compatible with Arduino IDE, Ideal for Projects Requiring Arduino Micro, 1pc by Kevin Harmon

The latest version of the Arduino IDE doesn't support them, so don't buy them thinking they're something like Arduino. The tutorials and instructions you have read are for casual users only. All you have to do is find "Arduino ide loading failed". You will see that there is a fatal bug in the Arduino IDE that prevents you from uploading board definitions for it. There are hundreds of open tickets on their site and thousands of people looking at their "solutions" but 99% of the solutions are due to being miraculously fixed. Without the Arduino IDE there's no good way to program it, so good luck getting it working as THEY DON'T WORK!