It does work in 1.20.4 you just download the schematic and paste it in your own world no matter the game version, the build only uses concrete, cyan glass and sea lanterns so nothing new that came in 1.21 :)
abfielder 24th June 2024
It's almost certainly fine in 1.20.4, just paste it into a creative world to test. The versioning on litematics can be taken with a pinch of salt.
