Hi all, I know this is an old thread, but for those of you still looking to create an alternative 'readonly-like' field, but don't want to use third party forms like Jotform (don't get me wrong, they DO have their place), you could try the 'dummy' field option. That is, create a new Airtable single line or long text field that contains the required data and display the that text field data in a separate form field with the appropriate 'READONLY' warning, and just don't use the data from that form field... it's readonly so your intention is that the back-end won't change on form submission.
I know this is inefficient and wasteful, but so is waiting for Airtable to create a 'readonly' form field.
If you find users are changing the 'readonly' form field and getting confused by the results, ie their fiddling doesn't change the form submission outcome, you might be able to sell them some training 😊
I use this method for displaying calculated summaries, as well as displaying calculated serial numbers, etc.