The correct answer was commented in Staging Ground by user @vincentdecaux:
"On Flowbite, they use a box shadow to make the "border" thicker. Keep a border-width at 1px, and add the CSS to your input:focus to have the same effect: box-shadow: tomato 0px 0px 0px 0px, tomato 0px 0px 0px 1px, rgba(0, 0, 0, 0) 0px 0px 0px 0px;
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