What techniques do y'all have for determining what the top-level URL is (not the domain, the full URL) when your code finds itself in a cross-domain iframe and therefore you don't have access to top.location or anything else useful in the top window object.
Occasionally you can find that parent.document.referrer is useful if you're an extra level down, or document.referrer if you're just one level below top. Occasionally ancestorOrigins can prove useful too. None of these is totally reliable though, so trying to get everything you can, in sequence, seems appropriate.
Are there any new API's in the last couple of years I maybe unaware of perhaps. Or a dev API of some kind. Luckily I don't have to care about Internet Explorer anymore. I'm hoping nobody marks this as a duplicate, because I'm hoping in 2022 there are new answers.
No.
For privacy and security reasons, browsers have become increasingly restricted over what referrer information they they pass across origins. Not, as you desire, laxer.