If you want change map you need delete old world folder
Download new world what you want and upload it to the server folder. it must be just folder, if it in .zip unzip it, world must be named "world" or change name in s2e
There may be another point of appearance on the server, you can go to the map in single player and see the coordinates of where something is built there, and then check these coordinates on the server
For some, this is a complicated instruction, you do not need to move the downloaded map to the world folder
You need download map for example it`s named "Eo_Ethaerith_Aeriveth", put it minecraft-server-1.21 folder, delete "world" folder and rename your "Eo_Ethaerith_Aeriveth" to "world".
Search in server.properties level-type=
Determines the world preset that is generated.
Escaping ":" is required when using a world preset ID, and the vanilla world preset ID's namespace (minecraft can be omitted.
minecraft:normal - Standard world with hills, valleys, water, etc.minecraft:flat - A flat world with no features, can be modified with generator-settings.minecraft:large_biomes - Same as default but all biomes are larger.minecraft:amplified - Same as default but world-generation height limit is increased.minecraft:single_biome_surface - A buffet world which the entire overworld consists of one biome, can be modified with generator-settings.buffet - Only for 1.15 or before. Same as default unless generator-settings is set.default_1_1 - Only for 1.15 or before. Same as default, but counted as a different world type.customized - Only for 1.15 or before. After 1.13, this value is no different than default, but in 1.12 and before, it could be used to create a completely custom world.
can be omitted.