Hello,
Have you tried this approach?
JohnPlunkett_1-1712262154864.png
JohnPlunkett_0-1712262136792.png
.<= today()
Reference
https://doc.arcgis.com/en/survey123/desktop/create-surveys/xlsformformulas.htm
Constraints
Adding a constraint to a survey question restricts the accepted inputs for a response. This can include a specific range of numbers, combinations of letters and numbers, or general pattern matching. In your spreadsheet, the constraint expression is entered into the constraint field and informational text is entered into the constraint_message column of the survey worksheet. In the constraint expression, the input for the question is always represented by a period.
For example, you can use the following formula to restrict the input of an integer field to positive numbers only:
.>= 0
This formula, when applied to a date field, prevents the user from entering a value earlier than today:
.>= today()
You can also use calculations in constraints. This formula performs a calculation to only allow the user to select dates between today and 14 days from today:
(.>= today()) and (.<=(today() + (1000 * 60 * 60 * 24 * 14)))