Should I sell it? Is there anything interesting people who no longer game do with their machines?
Ideas:
Install Gentoo (not a joke! I have a 22 core CPU and it really helps)
Do heavy video processing.
Get a 4 channel TV Tuner card and a lifetime Plex membership, and use it to DVR OTA broadcast. Transcode them, which is where a beefy machine comes in - the default ts format takes up too much space. Lots of good shows on PBS. And as much as people complain about Plex, there is no good substitute for their DVR service.
Can the GPU be used for ML applications? Things like Stable Diffusion? If so, go wild with it.
If you keen to help the world, you can do some seti@home stuff. Or, setup a Tor node..
Otherwise, just keep it. In 10 years it will be not a powerful computer anymore. Or give it to some NGO or some other guys