Magento 2.3 Minicart check if subtotal is above value

You can have following knockout code in html file to achieve your desired result.

<!-- ko if: cart().subtotalAmount < 29.95 -->
    <span>custom message if subtotal is less then 29.95</span>
<!-- /ko -->

<!-- ko if: cart().subtotalAmount > 29.95 -->
    <span>custom message if subtotal is greater then 29.95</span>
<!-- /ko -->

Hope this helps.