[bityard]

As someone who does some (but not a lot of) web development, I guess the only thing I care about is: can I turn this off with uBlock Origin?

[KMnO4]

That’s like asking if you can turn off <form>s. Not sure why you’d want to. It’s a perfectly reasonable component that doesn’t need to be abused for ads.

[clementmas]

I use <dialog> a lot when building websites. I don't run any ads nor promotional content so if that element was blocked it would break lots of features.

[limbero]

Seems like you could, since it has an attribute and a pseudo class to select on. document.querySelectorAll("[popover]:popover-open") should select all visible popovers. AFAIK uBlock uses regular CSS selectors.

[tootie]

Nope. Not if the pop-up is first party.

[anamexis]

Yes you can - uBlock Origin lets you apply CSS rules, and popovers can easily be hidden with the [popover] selector.