Where do I have to live to qualify for a Swiss G cross-border commuter permit?

The G permit is specifically for cross-border commuters, so your main place of residence must be outside Switzerland. For EU/EFTA nationals, you must live in an EU/EFTA state and have your employment or self-employed activity based in Switzerland. The defining condition is the return requirement: you must return to your foreign place of residence as a rule every day, or at least once per week. If you stop returning regularly, you no longer meet the commuter conditions and may need a different type of permit.