Version 4 is a major change and the configuration file it creates is not
compatible with Plover 3 or earlier. Please backup your plover.cfg.
plover is built for Intel macOS and so requires Rosetta 2 to be installed.
You can install Rosetta 2 with:
softwareupdate --install-rosetta --agree-to-license
Note that it is very difficult to remove Rosetta 2 once it is installed.