How to Disable the Nether on a Minecraft Bedrock Server
Unlike Java Edition, Bedrock servers have no setting in server.properties to disable the Nether. Instead, you have to block access to the dimension in a different way.
Options
Behavior pack
You can create or install a behavior pack that blocks Nether portals from being created or disables their functionality. Upload behavior packs as described in Add Behavior and Resource Packs and enable them for the world.
Command block
With a command block in a loaded chunk you can automatically teleport players back to the overworld whenever they enter the Nether. Example:
/execute as @a[m=!c] in minecraft:nether run tp @s ~ ~ ~ minecraft:overworld/execute as @a[m=!c] in minecraft:nether run tp @s ~ ~ ~ minecraft:overworldThe command block must run in Repeat mode with Always Active enabled so the command is executed continuously.
Note
Both methods are workarounds — the Nether itself cannot be fully disabled on Bedrock, only access to it can be restricted.