SOURCE

document.addEventListener('DOMContentLoaded', () => {
    const iframe = document.createElement('iframe');
    iframe.setAttribute('sandbox', 'allow-scripts allow-same-origin');
    iframe.style.width = '100%';
    iframe.style.height = '100%';

    const iframeContainer = document.querySelector('.iframe-container');
    iframeContainer.appendChild(iframe);

    iframe.contentWindow.document.body.style.overflow = 'hidden';

    const style = document.createElement('style');
    style.textContent = `
        html, body {
            touch-action: auto;
        }
    `;
    iframe.contentWindow.document.head.appendChild(style);

    const inner = document.createElement('div');
    inner.style.cssText = `
        height: 100%;
        overflow: auto;
        // overscroll-behavior: none;
        -webkit-overflow-scrolling: touch;
    `;

    iframe.contentWindow.document.body.appendChild(inner);

    const container = document.createElement('div');
    document.body.appendChild(container);

    const arr = new Array(20).fill(0);
    arr.forEach((_, i) => {
        const item1 = document.createElement('li');
        item1.textContent = `iframe 第 ${i+1} 项`;
        inner.append(item1);

        const item2 = document.createElement('li');
        item2.textContent = `外部 第 ${i+1} 项`;
        container.append(item2);
    });
});

<div class="iframe-container"></div>

.iframe-container {
    -webkit-overflow-scrolling: touch;
    width: 100%;
    height: 100%;
}