part of the issue with 'bubbles', as I see it, is that you don't know you're in a bubble. a big huge honking option of "keep me in the bubble" and "show results outside my bubble" would make it a lot more obvious (and manageable) to many people who are oblivious to the notion that they live in an information bubble. won't stop people who only use one source of news, but in a search aspect, it would be useful.
Interestingly, Google themselves seem to be at least somewhat aware of this - though it may just be an accidental side effect of trying to drive user engagement on YouTube.
I’ve been noticing an occasional “Show me something new to me” prompt showing up in my YT feed. It has literally never provided anything I was interested in watching, but I appreciate that they’re trying to burst bubbles.