Minecraft considers sea level to be at block 62, and clouds start generating at block 128. Most ores are found below sea level, and no ores will be found above cloud level.

After a beacon is made, it must be set on top of blocks of netherite, emerald, diamond, gold, or iron. The beacon's capabilities will not be impacted by the type of earth material.

Since the launch of 1.17, diamond ore has been generating one block off of where it should have been in Java Edition. That's getting fixed in Java 1.17.1.