[skymer]

The paper shows that it is essentially impossible for an adult male to get the recommended DI of magnesium (420 mg/day) by eating vegetables alone. As far as I can see, the paper does not resolve whether that target is too high, or whether it can be reached by eating meat or taking supplements.

[cageface]

Seeds are a great source of magnesium. Pumpkin seeds in particular have a lot of it and are inexpensive and tasty.

[skymer]

The paper says "The highest food sources of magnesium are leafy greens (78 mg/serving), nuts (80 mg/serving), and whole grains (46 mg/serving)..."

So five servings every day of nuts and/or leafy greens would do it, but that doesn't sound like anybody's typical diet.

[duckmysick]

The same paper also says "[...] foods containing phytates, polyphenols and oxalic acid, such as rice and nuts, all contribute to magnesium deficiency due to their ability to bind magnesium to produce insoluble precipitates, thus negatively impacting magnesium availability and absorption."

[opportune]

A typical serving of leafy greens is quite small, an adult can easily eat 2-4 servings at a time after they've been cooked.