Re: "Siri AI still "updating" on MacOS 27.2".
It seems MacOS 27 was a very major upgrade. Much goes on in the background after the initial installation. Eg: Spotlight re-indexes everything when it can do so. Integration of Apple Intelligence features may also continue with MacOS 27.2.
(ie: See: What's new in the updates for macOS 27 Golden Gate)
Where practical, leaving intensive work (like video-editing, etc.) till later, and leaving the Mac connected and plugged into power, especially overnight, can be helpful in allowing the upgrade / update process to complete more quickly and simply.
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Re: Anyone else having this issue or found a way to resolve?
As Apple customers, like yourself, we don't get to see what feedback is sent or discussed with Apple. Seems patience is most likely the way to "heal" the situation.
Many have had no problem with the updates, and we hear more from those who have. Some have chosen the option to use Siri "Classic" instead of Siri "AI" for now, postponing access to the new features till later.