Stronghold can generate on the surface. Not above it, just the grass can be replaced with these bricks.
Seed: -7495965361695381205 Coordinates: /execute in minecraft:overworld run tp @s 2151.96 63.00 834.47 61.05 24.75
MC-141986 Stronghold can generate above surface
MC-233493 Strongholds Rarely Spawn Excessively High Above the Surface