https://www.arduino.cc/reference/en/libraries/keyboard/

Arduino Uno/Mega/Nano are included in the compatibility list even though they are not compatible with the Keyboard library.

Additional context

Additional reports

• Arduino IoT Cloud Docs arduino-libraries/ArduinoIoTCloud#380 (comment)
• https://forum.arduino.cc/t/arduino-keyboard-not-working-on-arduino-uno-r3/1102400
• https://forum.arduino.cc/t/documentation-for-keyboard-library-needs-some-correction/1126221
• https://forum.arduino.cc/t/sketch-funktioniert-nicht-keyboard/1099364/6
• https://forum.arduino.cc/t/issue-on-keyboard-library/1065385
• https://forum.arduino.cc/t/what-is-wrong-here/1080550/7
• https://forum.arduino.cc/t/why-is-arduino-nano-usable-as-usb-keyboard-controller/1333682