Hi, I am trying to fix Largest contentful paint element. Where to edit Wallpaper Carousel Widget template?

You cannot directly edit templates on version 5. Please could you provide more information on exactly what you are trying to do?

I want to add a few attributes to the <img> in Images Widget

Attributes: width, height and fetchpriority

You would indeed need modification for that. Maybe something like using javascript to replace that element with what you need (certainly not my area of expertise)

I will try that way. Where to access the default template? (it was easier on the V4)

I tried this and it worked.

document.addEventListener('DOMContentLoaded', function() {
    document.querySelectorAll('img').forEach(img => {
        img.setAttribute('fetchpriority', 'high');
    });
});

That code will update all images, not just the ones inside the widget.

 

That code will update all images, not just the ones inside the widget.

Yes, you are correct. One can customize it further for whichever image they want.