Need to spec out how inert subtrees are exposed to AT. Dialog-backed inert content perhaps makes no interest for screen readers and may be safely cut off, however screen magnifiers might need it. HTML:inert, which is re-added in [1], seems adds a bunch of new use cases which vary from offscreen accessible elements to image carousel controls, thus I'm not quite sure what mapping could make the best experience for AT.

Note, inert subtrees spec [2] allows user agents to override the restrictions on search and text selection in inert subtrees, which may speak out against cut-off approach.

Perhaps, the safest thing to do is to expose an accessible state or object attribute in case of ATK/IA2 on inert subtrees to let AT to decide how to deal with inert content.

Thoughts?

cc'ing @jcsteh, @MarcoZehe, @alice, @cookiecrook

[1] https://github.com/alice/html/tree/re-add-inert
[2] https://html.spec.whatwg.org/multipage/interaction.html#inert-subtrees