Based on nothing more than my own observations, it seems that the tethering network range will be 192.168.0.x if that’s not being used by eth0 and/or wlan0, or 192.168.1.x if 192.168.0.x is already being used.
There was a recent thread where DHCP might not have been passing the DNS IP addresses to the tethered devices. Unfortunately, it was not 100% clear if the problem was with connman or the OP’s network. In your case, are the tethered devicess able to ping an IP address, eg 1.1.1.1?