I'm surprised Bahrain isn't on this list. It's highest hill is only 134 m tall, I would have thought the rest of the island would drag the average down far enough.
And Bahrain has over 39% of it's land under 5 m, (https://en.actualitix.com/chart/bhr/bahrain-land-area-where-elevation-is-below-5-meters.png) so that means a maximum average elevation of 83.7 m at most (0.39*5+0.61*134). So it should be on this list.