How do I schedule a text to an Android user from my MacBook Air?

Any device that can receive iMessages. Scheduling is specifically related to iMessage, not SMS messaging.

It its clarifying that any Apple device running any OS version that can still receive iMessages will get the scheduled message. It does not require the recipient be running a specific version of their device's OS.

You cannot.

The option to schedule messages only works with iMessages. It does not even work on an iPhone with SMS messages.

click here ➜ Schedule a message on Mac to send later - Apple Support

I think we run in the classic misunderstanding of the difference between Message and iMessage.

The link you're given refers to Apple's iMessage.

Messages (green) you can't schedule.