I've a similar question like Rob.
After one week out of office I scanned over the Project Cortex resources (or better it was my intention to do so).
But Project Cortex resources seems to be removed - and partly replaced by knowledge-content-services resources.
And details like the recordings and slides for previous Project Cortex Office Hours seems to be no longer available. I collected what I found below.
Is there any announcement about what happens with Project Cortex?
I cannot imagine that was completely absorbed by Microsoft Viva. I see just one intersection --> Viva Topics. But Topics are important at many places - not only for usage in Teams.
Affected resources are
Project Cortex Resource Center
https://resources.techcommunity.microsoft.com/project-cortex-microsoft-365/
may be replaced by:
https://resources.techcommunity.microsoft.com/knowledge-content-services/
Project Cortex Blog
https://techcommunity.microsoft.com/t5/project-cortex-blog/bg-p/ProjectCortexBlog
may be replaced by:
https://techcommunity.microsoft.com/t5/knowledge-and-content-services/bg-p/KnowledgeAndContentServicesBlog
Project Cortex Office Hours
https://resources.techcommunity.microsoft.com/knowledge-content-servicesproject-cortex-office-hours/
replaced by ?
https://resources.techcommunity.microsoft.com/webinars/ (and here the Category Project Cortex)