"Good enough" for what, exactly?
There isn't any absolute set minimum amount. Do as much or as little exercise as you can, are interested in doing, and can maintain for a lifetime pattern. Adjust diet accordingly.
If you are told you "must exercise an hour a day" will you keep that up long term if you only like doing 20 minutes a couple of times a week? You'll start with a hiss and a roar and soon stop.
If you like doing 20 minutes 3x a week and someone tells you "10 minutes once is enough" would you stop?
What's the "enough" about, enough for what? Exercise doesn't make you lose weight. Diet does.
Exercise keeps you fit and healthy. Best health is achieved with 30-60 minutes of some form of activity most days, on average. If you're not at a point where you can exercise that much yet, you might choose to do less for now and simply eat a little lower. As you improve your fitness, you'll be able to cope with doing more, and may be interested in increasing your fitness minutes.
Deb, in New Zealand