[PLUG] question on how to fix a mysterious DNS address problem

[MC_Sequoia]

"running a nmcli command showed me where the VPN address is coming from

nmcli --show-secrets connection show tun0

...lot of output including

ipv4.addresses:                         10.18.0.38/16
ipv4.gateway:                           10.18.0.1

So my openSuse Leap 15.4 system using Network Manager and the openvpn
built in component is setting up the address into the /etc/resolv.conf file.

Apparently this VPN is useless to my Netgear c6300v2 cable modem/router
as at this point in time, I don't believe the router has anyway of
connecting to the vpn tunnel."

I very strongly suspect you don't understand any of this. There's no VPN involved here. 

That "ipv,gateway" address is the LAN side ip address of your Netgear router. Your PC is configured to use DHCP to configure DNS via the LAN gateway device. 

This is all very standard default out of the box pc & network router configuration.

When your pc wants to go to Google.com, it sends a DNS resolve query to the the network gateway, which then proxies that query to the Internet side of the the network gateway that by standard default configuration gets its DNS from via DHCP from your ISP. 

There's nothing mysterious, VPN, secret, etc. This is all very standard default out of the box workings of DHCP and DNS.