I've tried using fit-content, fill-content, height="100%", and height="auto" I'm not sure if this is possible, but if it's not google definitely should try and figure out a way to make it work.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="./style.css">
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js"
integrity="sha384-U1DAWAznBHeqEIlVSCgzq+c9gqGAJn5c/t99JyeKa9xxaYpSvHU5awsuZVVFIhvj"
crossorigin="anonymous"></script>
<title>Document</title>
</head>
<body>
<iframe
src="https://docs.google.com/spreadsheets/d/e/2PACX-1vR-p4uEH_VDK55IPAhz94TLM03oZ40dis2blDnH_vm31QC8BaqqO0VvZU9c3u_EHS0WB8z1O92NDiae/pubhtml?gid=0&single=true&widget=true&headers=false"
width="100%" height="fill-content"></iframe>
</body>
</html>
You cannot change the style of an external iframe with internal CSS. Like many other Google embeds, Google Sheets does not give you the option to make the embed responsive.