Global Income Coin is an economic model carrying a monetary policy (i.e. the bottom-up distribution of newly created money), not a technology. We do not inherently care on what platform we implement it, and will try to use existing technologies rather than developing our own. We do want to get started, so we're choosing technology that works today over technology that works tomorrow.

Lightning is promising. The first tether transaction on lightning was only a month ago, however [1]. So that's not yet a boring enough solution.

Ethereum and Polygon won't (today) scale worldwide, but if we're able to gain traction we'll (a) branch out to every other network if necessary (b) contribute to networks so they can start to get to global scale

[1] https://bitcoinmagazine.com/technical/tether-sent-using-the-...