What is the best way to initialize formData in @rjsf/material-ui-v5

[dagda1]

What is the best way to initialize form data in @rjsf/core-v5?

If I pass 3 fields that are undefined when the form loads, how can I get them into the formData?

If not, is the only way to use formData?

<Form
   formData={{
     field1: undefined,
     field2: undefined,
     field3: undefined

Has this behaviour changed between v4 and v5?

[aress31]

Bump, I am interested to know too, additionally how to initialise specific fields, using, should one use the onChange?