Ah! Encontrei a razão porque não obtinha resultados, para o scan dos 256 endereços, usei 192.168.1.0-255 em vez de 192.168.1.0/255.
Assim sem hostnames definidos em hosts (ou qualquer outro DNS local), os resultados nmap são:
Nmap scan report for NOSdrive (192.168.1.1)
Host is up (0.034s latency).
Nmap scan report for 192.168.1.2
Host is up (0.21s latency).
Nmap scan report for 192.168.1.100
Host is up (0.14s latency).
Nmap scan report for 192.168.1.101
Host is up (0.00046s latency).
Nmap scan report for 192.168.1.102
Host is up (0.12s latency).
Nmap done: 256 IP addresses (5 hosts up) scanned in 73.78 seconds
e com os nomes definidos em hosts:
Starting Nmap 7.94 ( https://nmap.org ) at 2025-04-22 22:06 WEST
Nmap scan report for NOSdrive (192.168.1.1)
Host is up (0.78s latency).
Nmap scan report for 192.168.1.2
Host is up (0.29s latency).
Nmap scan report for hp (192.168.1.100)
Host is up (0.14s latency).
Nmap scan report for leg (192.168.1.101)
Host is up (0.00081s latency).
Nmap scan report for rpi4 (192.168.1.102)
Host is up (0.14s latency).
Nmap done: 256 IP addresses (5 hosts up) scanned in 114.98 seconds
Resultados identicos com o seu script.
Obrigado