Just a guess, but Buffett would often host undergrad and grad students at his home.

https://www.nasdaq.com/articles/warren-buffett-hosts-15-whar...

FWIW, in 2015 I happened to be in Omaha and I made a point to try and at least "see" it. It's just in a regular neighborhood. I parked up the street and, trying not to be too intrusive, I just walked by it.

The only unusual element I saw were some ropes deliberately blocking off the driveway. From a prior news article, I was aware he employed a PSD, but I didn't see any obvious security presence on the property--likely they're very deliberately low-key.