A one-line to check IPv6 devices on your LAN:
$ ping6 -c3 -I wlan0 ff02::1 | awk ' /bytes from/ { print $4 }' | sort -u | sed 's/:$//'
fe80::1af4:6aff:fe9c:ced4
fe80::212:40ff:fe8a:8e38
fe80::66d1:a3ff:fe31:9c57
fe80::c24a:ff:fe2c:dcbc
fe80::d263:b4ff:fe00:2a61
So: 5 IPv6-enabled devices on my LAN. At least: 5 devices that react on the broadcast ping6.
You can feed that into ping6 to see if they are ping6-able:
$ ping6 -c3 -I wlan0 ff02::1 | awk ' /bytes from/ { print $4 }' | sort -u | sed 's/:$//' | awk '{ print "ping6 -c3 -I wlan0 " $1 }' | /bin/sh | awk ' /PING/ { print $2 } /packets transmitted/ { print $0 "\n" } '
fe80::1af4:6aff:fe9c:ced4(fe80::1af4:6aff:fe9c:ced4)
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
fe80::212:40ff:fe8a:8e38(fe80::212:40ff:fe8a:8e38)
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
fe80::66d1:a3ff:fe31:9c57(fe80::66d1:a3ff:fe31:9c57)
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
fe80::c24a:ff:fe2c:dcbc(fe80::c24a:ff:fe2c:dcbc)
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
fe80::d263:b4ff:fe00:2a61(fe80::d263:b4ff:fe00:2a61)
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
So ... they are all ping6-able.
