Yeah I think you may have better luck with butlerd https://github.com/itchio/butler/tree/master/butlerd - basically butler is a command line interface to butlerd which is a daemon with JSON RPC interface. I did not try it myself, but the docs seem to be pretty comprehensive https://docs.itch.ovh/butlerd/master/ .
GameHub launcher apparently uses butlerd for itch.io integration https://github.com/tkashkin/GameHub/tree/master/src/data/sources/itch