If I understand your network setup correctly, NetBIOS hostnames do not propagate over VPN nor across subnets.
You can try adding an entry to the client device hosts file that maps the “Nextcloud hostname” to 192.168.0.201, but that would need to be done on every client device.
Alternatively, you can try adding the same mapping on the router via LuCI → Network → Hostnames that may work across all client devices.
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