This is like seeing some aging movie star on TV that I thought was dead for years
Forth needs a big stack which means lots of SRAM.
Would there be any advantage of using it on an Atmega328 chip compared with the Arduino C++ system?
You would not be using the IDE - the serial monitor does not have the necessary functionality to load and save code. The advantage is continuous but fast interpretation - you instruct it to do something and that happens virtually instantly, you construct pieces and try them out one after the other in a continuous flow.
I used to think (maybe still do) that Forth was a very clever concept but I suspect that in reality it would be a lot more work to use than Arduino C++
Is it possible?