It seems the War Within is the first expansion in a while without any dungeon meta-achievement.
In Dragonflight, we’ve had the Glory of the Dragonflight Hero achievement that rewards Shellack. Glory of the Shadowlands Hero in the Shadowlands expansion rewarded the Voracious Gorger mount. In Battle for Azeroth, completing Glory of the Wartorn Hero granted the Reins of the Obsidian Krolusk mount, and so on.
Oddly enough, Blizzard has not added any dungeon meta-achievement in the War Within, and Early Access starts in just 10 days. Patch 11.0.2 is going live this week, so it’s very unlikely we’ll see any sweeping changes to achievements before the new expansion goes live.