Do wireless keyboards send data to the computer using microwave frequencies?

Whether a wireless computer keyboard uses microwave frequencies for communication with the computer depends on the technology used by the keyboard, and on the definition of microwave frequencies.

Wikipedia defines microwave frequencies to be in the 1...30GHz range. Many wireless keyboards operate in the 2.4GHz band, which would make them microwave transmitters (and receivers). Other keyboards use different frequencies, below 1GHz. Those would not be microwave devices, according to this definition.

The 802.15.4 standard, for example, lists a 868.0-868.6MHz band (Europe), 902..928MHz (US) and the 2.4GHz (2400...2483.5 MHz) band (worldwide, but subject to regional restrictions).