Hello Indexofrefraction, yes, I know server/client side difference. Indeed, article mentions meta would be generated server side in what seems to be Python, though index.php as you mention may work as well.
Now, what I don't have a clue is about URL update. I've seen a couple of tours here where "folder structure" seems to be present when in fact it seems to be updated the same way as current krpano's deeplinking by javascript on client side. If query is not used then same way would work, or PHP would be needed. Any idea? What would be needed is that URL generated meta could match what USER AGENTS see, that's the thing.
About what I mention for KRPANO is that I if a global solution (including PHP) could be added to the "kit", that would be very useful for everyone, as currently only people that develops this can access the feature. If I get it I don't disregard selling it as a plugin, I know many people would appreciate this (I definitely would buy it), though would be very nice to count on that one as the current deeplinking has the limitations I mention, which basically will affect anyone sending a whatsapp, Linkedin message and probably many other platforms.
I'd appreciate anyone else's insight about this subject.
Best