inert attribute would allow web authors to mark parts of the DOM tree as inert:
When a node is inert, then the user agent must act as if the node was absent for the purposes of targeting user interaction events, may ignore the node for the purposes of text search user interfaces (commonly known as "find in page"), and may prevent the user from selecting text in that node.
Furthermore, a node which is inert should also be hidden from assistive technology.
Check out the brief, yet comprehensive, inert explainer.
Try out the polyfill.
See it in action on a11ycasts.
What do you think?
My slightly biased opinion: this seems like extremely low-hanging fruit for keyboard accessibility. It's easy to understand, not too difficult to implement on the browser side, bundles a bunch of useful functionality together yet remains primitive enough to be flexible. It solves a real problem which has existed for a long time and which today has no straightforward solution.
We're explicitly looking for implementer interest from other browsers, but any feedback would be welcome. Developers: do you have questions/concerns? Is there more we can add (examples, edge cases, etc) to bolster the case? Browser representatives: is there anything technically blocking you from implementing this as outlined in the explainer?