If you are using a Loop Grid Widget and not the Posts Widget, you can use this smaller snippet (as long as you can put the 'dynamic-ellipsis' class directly on the text widget:

<script>
    document.addEventListener("DOMContentLoaded", function() {
    const excerpts = document.querySelectorAll('.dynamic-ellipsis');

    excerpts.forEach(function(excerpt) {
        const maxLength = 150; // Set this to the number of characters you want to show
        const text = excerpt.innerText.trim();

        if (text.length > maxLength) {
            const truncatedText = text.slice(0, maxLength);
            excerpt.innerText = `${truncatedText}...`;
        }
    });
});
</script>

If you are using the Elementor Posts Widget and/or the Loop Grid widget then use this code. For the Posts Widget, select the widget, go to the 'Advanced' tab, and enter 'dynamic-ellipsis' in the class field (no quote marks), then using the following script instead. This will cover both use cases and is the more versatile snippet:

<script>
document.addEventListener("DOMContentLoaded", function() {
    const excerpts = document.querySelectorAll('.dynamic-ellipsis');

    excerpts.forEach(function(excerpt) {
        const maxLength = 150; // Set this to the number of characters you want to show
        let textElements;

        if (excerpt.classList.contains('elementor-widget-posts')) {
            textElements = excerpt.querySelectorAll('.elementor-post__excerpt p');
        } else {
            textElements = [excerpt];
        }

        textElements.forEach(function(textElement) {
            const text = textElement.innerText.trim();

            if (text.length > maxLength) {
                const truncatedText = text.slice(0, maxLength);
                textElement.innerText = `${truncatedText}...`;
            }
        });
    });
});
</script>