I have a coworker who does this and I’ve found saying ‘oh neat…’ is the perfect response. It’s positive, but only slightly. And if you use it repetitively it will become very obvious you don’t give a shit, but you’ll never get called on it.

I had a great weekend. I hung out with a friend and we went out to dinner.

Oh cool. Yeah I got out all the time. This weekend I went to this crazy place that’s super hard to get into. We got right in. It was awesome.

Oh…neat…

Works every time