I'm going to be frank with you; I have literally no conception of what a "buckler" is beyond "easier to wield/lighter shield that provides a minor defensive advantage". I have no idea if any of that is even accurate to begin with, and furthermore no idea what the history of bucklers in D&D are. None whatsoever.
I needed "smaller easier to wield shield" for a few magic items I was creating though, so here come the bucklers.
You probably get the idea to begin with here. Spend part of your action to position the buckler for a minor AC boost. Doesn't offer you the constant protection of a shield, but allows you to wield two handed weapons with said shield equipped. I definitely see these as being useful for anyone with the Shield Master Feat, as you'd retain those benefits even if your character wasn't in a defensive stance.
Something I ought to say though, the Vine Buckler is more the "default" for this type of shield. Spending your object interaction for a +1 to AC is fairly powerful, especially if you can use two handed weapons in the meantime. Spending a bonus action for that benefit is a little more reasonable I feel, falling behind shields in utility when it comes to action economy and defensive capacity but offering more versatility in your choice of weapon. It can also then be more on par with a shield in its defensive capacity if the character takes the Shield Master Feat (as previously mentioned).
That's the purpose of the Spriggan Buckler's Enchantment, by the way. It molds to your arm until you command it otherwise, further freeing your action economy for the same benefit as a "normal" buckler. Object Interactions vs Bonus Actions.