looking at the final outputted HTML code, it looks like v5.7 causes the select statement to be closed before the option statements:
embedded HTML in the CF7 form:
<select id="s_PricingYear" onchange="UpdateProgramCostHandler()"><option selected>2022</option><option>2023</option></select>
expanded to the following in the final html page:
<p><select id="s_PricingYear" onchange="UpdateProgramCostHandler()"></select>
</p>
<option selected="">2022
</option>
<option>2023
</option>