Hi,
Try adding:
FallbackNameservers = 192.168.0.1
To /etc/connman.conf
Then reboot or restart the connman.service.
Not sure if this will, but below link suggests fallback nameservers are used with tethering:
https://connman.moblin.narkive.com/7ESKZpCw/configuring-dhcp-server
Thanks Tom.