Anyone have any idea if this still works in 1.20.x?

gumwyrm thats not entirely true, matter of fact it quite the opposite. the hotter you heat it the softer it becomes, something about annealing the copper makes it softer overall.

Might I suggest adding a way to make a workable chunk of copper using native copper nuggets without needing to "smelt" the already effectively pure copper? Perhaps 20 nuggets and a rock to get a stack of small sheets, which you then forge into an ingot at 600C+ as an example.

Addition: It occurred to me after making this comment that the idea would only be mildly useful as things are normally, but the addition of a stone anvil like Tsimshianic suggested and a wood mallet or stone hammer would really make it worth the effort

this actually makes copper useful late-game lol

I think it would be great to have a Stone Anvil to complement this mod. 

OmegaHaxors

copper work hardens, so no... not particularly realistic. yes, it is ductile enough to cold-forge, but you would make a fragile end product from introducing defects into the structure of the metal.

Ethanol_Balls Just try?

does this work for 1.18.x?

Huh not only is this realistic but is also balanced because you still need to make the anvil which requires casting anyway.