Same output on router and client:
sudo tcpdump port 123
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on wlan0, link-type EN10MB (Ethernet), capture size 262144 bytes
On the client
$ sudo ntpdate -q localhost
16 Mar 15:44:46 ntpdate[14071]: no server suitable for synchronization found
$ sudo ntpdate -q 0.openwrt.pool.ntp.org
server 195.186.1.101, stratum 2, offset 0.942723, delay 0.04248
server 178.209.53.202, stratum 2, offset 0.935283, delay 0.06239
server 162.159.200.123, stratum 3, offset 0.941215, delay 0.04973
server 82.197.188.130, stratum 2, offset 0.944880, delay 0.04431
16 Mar 15:45:39 ntpdate[14093]: step time server 195.186.1.101 offset 0.942723 sec
$ sudo ntpdate -q 1.openwrt.pool.ntp.org
server 162.159.200.123, stratum 3, offset 0.939904, delay 0.04980
server 45.157.190.152, stratum 3, offset 0.936377, delay 0.05733
server 162.159.200.1, stratum 3, offset 0.940961, delay 0.05429
server 192.33.214.47, stratum 2, offset 0.940969, delay 0.04736
16 Mar 15:45:57 ntpdate[14095]: step time server 192.33.214.47 offset 0.940969 sec
Nothing is happening on port 123. Apparently, the NTP server is not running.
Check:
cat /etc/config/system |grep server
config timeserver 'ntp'
list server '0.openwrt.pool.ntp.org'
list server '1.openwrt.pool.ntp.org'
list server '2.openwrt.pool.ntp.org'
list server '3.openwrt.pool.ntp.org'
option enable_server '1'