While there are no form elements like text inputs, checkboxes, select lists or other form elements in Adobe XD at this time there are multiple ways to create and export forms.
The following examples show provide examples of forms.
Example Projects
xd-examples/web-export/examples/form-elements at master · velara3/xd-examples
GitHub
Standard Forms
xd-examples/web-export/examples/material-design at master · velara3/xd-examples
GitHub
Material Design form components
xd-examples/web-export/examples/spectrum-components at master · velara3/xd-examples