Gifted Escapist achievement in AC Mirage

If you're looking to get this done and out of the way all in one go, I've found the Excavation Site to be the best spot since there are 3 scaffolds bundled together that you can grind for the achievement.

During the Find the Missing Brother case under the Ahmad ibn Musa investigation you visit the Excavation Site in the SW portion of the Baghdad wilderness, in the centre of the excavation site you'll find 3 scaffolds.

I suggest that you complete the case/mission first so that you can focus on the achievement. Afterwards simply destroy the scaffolding and then leave the restricted area. Now, there are two ways to respawn the scaffolding:

#1 - Call your camel/horse and ride to the nearby viewpoint (located north-east of the excavation site) to force the scaffolding to respawn and then rinse and repeat this until you've collapsed 20 scaffolds.

#2 - Fast travel to the above mentioned viewpoint to respawn the scaffolding and then once again rinse and repeat this method until the achievement unlocks. (Remember you can only fast travel outside of conflict so the first method will likely be the go-to. However, it is possible to collapse the scaffolding and leave without entering conflict, in which case fast traveling would be quicker)

Here is a game clip I recorded to show the spot and method:

Big thanks to Dr Scruffleton, iSanket, Bob Wings and Temppuli for their comments and information in helping to fine tune this solution.

Bug warning:
Unfortunately as of 11/10/2023 it seems this achievement can be buggy. Your achievement tracker might not track correctly and you may need to collapse more scaffolding than the required amount in order to unlock this achievement, or in the worst case scenario your tracker may stop working all together in which case the achievement will not unlock. You might be able to fix the tracker by closing and relaunching the game, hard resetting your console, deleting and reinstalling the game, and lastly deleting your save file and starting a new game (I suggest to try this only after you've unlocked every other achievement first). If you've tried all of the fixes above and it still hasn't unlocked you may need to wait for Ubisoft to release a fix/update.