This is likely old news to most of the people following me on here, but where Steam collects 30% of a game's revenue, Itch only asks for a 10% share and that's a voluntary split; devs can set that to 0%. I usually check if a game is available on itch before buying so more money goes to the devs.
I love what itch is trying to be, but if there’s one piece of advice I could give first-time gamedevs, it’s to focus on other storefronts. itch is a fantastic place for demos, but almost nobody buys games there. Pains me to see devs trying to make a living prioritize it over Steam.