Slitherine

I recently bought my first Deck, and this game was one of the first to install. English is not my preferred language, but I cannot change the language in game - the little flags on the first screen are absent on Deck but of course present on desktop/laptop. The language flags are there in the GOG version (via Heroic), but the controls are awful and I prefer Steam default. I have seen no way to change the language in the options. Is there anything to be done?