I'm using a library that turns things into ES6 Proxy objects, and another library that I think is choking because I'm passing it one of these (my code is a travesty, I know), and I couldn't figure out how to unProxy the Proxy object.
But I was just being dumb. Proxies can do anything!
For my use case (LWC), I used structuredClone. Creates a deep clone and doesn't require a library like lodash.
structuredClone(proxyObj);