Managing and enforcing security policies for devices and apps to protect organizational data through Intune
I also had the same issue, logged into Defender today after coming back from leave and found Advanced Hunting was missing. Luckily, I was able to see it in our Test tenancy. So, I copied half of the link from that and added my tenant ID. And now it has started showing in the Defender portal too.
https://security.microsoft.com/v2/advanced-hunting?tid=pasteyourtenantidhere