What's the difference between a keyboardist and a keyboarder?

A keyboarder is primarily defined as a typist, while a keyboardist is defined as a musician.

keyboarder
1. A panel of buttons used for typing and performing other functions on a computer or typewriter.
2. Music
a. A row of levers that are depressed with the fingers to produce or modulate the sound of an instrument, such as a piano or organ.
b. Any of various instruments, played by means of a musical keyboard, often connected to a synthesizer or amplifier.

https://www.thefreedictionary.com/keyboarder

keyboardist
a person who plays a keyboard instrument, esp an electronic musical instrument
https://www.thefreedictionary.com/keyboardist

The definition above is actually the entry for keyboard (noun), with the verb given as someone who uses a keyboard. For the verb, the first definition relates to input of information, the second to playing a musical instrument. The entry under that gives the related nouns (i. e., one who keyboards) as keyboarder and keyboardist, in that order. Which suggests exactly the distinction given in the response.

For confirmation, another dictionary offers this definition of keyboarder:

someone whose job is to put information into a computer using a keyboard

https://dictionary.cambridge.org/dictionary/english/keyboarder

Keyboardist is defined as one who plays a musical instrument that has a keyboard everywhere I could find - no ambiguities.