I'm sorry if I gave not enough details, but I thought you were more familiar with OBS. I never heard of this chair removal before and it caught my interest, so this is the way how I got to the answer. May be you can improve your search skills with it.
In the release notes you mention is this: "Added chair removal option for NVIDIA RTX Background Removal"
There was no background removal thing in my OBS, neither as source nor as filter nor anywhere else.
So I googled for "NVIDIA RTX Background Removal".
As second search result, I got a link to a thread in this very OBS forum:
https://obsproject.com/forum/threads/nvidia-background-removal.170155/
In this thread you find this solution link posted by someone who solved the same question:
https://www.nvidia.com/en-us/geforce/broadcasting/broadcast-sdk/resources/
We're looking for some video effect, so I downloaded the corresponding "video effects" package for the RTX graphics card I own and installed it.
Now I started OBS again, and now a "NVIDIA background removal" filter was available for video capture device (webcam) sources in OBS and I found the chair removal option in its settings after I added the filter to my webcam source.
So go to the Nvidia Broadcast download center at
https://www.nvidia.com/en-us/geforce/broadcasting/broadcast-sdk/resources/ and get the video effects package for your graphics card. This will add the Nvidia background removal filter in OBS which includes the option you're looking for.