From D&D Wiki
Wait, "Apart" of the Namekian race? So any race except for a Namekian can take this epic boon?
There is no way in official material to increase Dexterity beyond 20, and this is for good reason. Bound AC, a core principle of 5e, relies on Dex being capped at 20. The highest remotely possible AC a player-character can normally achieve is a 20th level barbarian with 20 Dex and 24 Con wielding a shield, and that's only 24 AC. That's extreme, and even official Epic Boons can't increase it above that. Almost any character with 30 Dex can achieve 24 AC with studded leather and a common shield, let alone a single magic armor--or God forbid a 20th level barbarian with 34 AC from maxed Dexterity and Constitution. Even a tarrasque, the baddest of the bad, can only hit that on a 15 or higher, and that's assuming that barbarian doesn't have a single magic item. Some ancient dragons would need nat 20s.