Looking at the DHCP from my cable modem, it is giving the router these:
DNS 1: 209.18.47.62
DNS 2: 209.18.47.63
So at least those are not being passed on to my client machines.
As an experiment I switched from Quad9 to CZ.NIC. Nothing changed. I switched it to Google, and rebooted the router, again nothing changed.
Wireshark DHCP ack capture:
Frame 544: 371 bytes on wire (2968 bits), 371 bytes captured (2968 bits) on interface \Device\NPF_{3C34E1A4-5939-462B-810B-CADA620C7C08}, id 0
Ethernet II, Src: CZNICzsp_00:43:b9 (d8:58:d7:xx:xx:xx), Dst: TRENDnet_ed:73:32 (3c:8c:xx:xx:xx:xx)
Internet Protocol Version 4, Src: 192.168.1.1, Dst: 192.168.1.12
User Datagram Protocol, Src Port: 67, Dst Port: 68
Dynamic Host Configuration Protocol (ACK)
Message type: Boot Reply (2)
Hardware type: Ethernet (0x01)
Hardware address length: 6
Hops: 0
Transaction ID: 0xe24c39d2
Seconds elapsed: 0
Bootp flags: 0x0000 (Unicast)
Client IP address: 192.168.1.12
Your (client) IP address: 192.168.1.12
Next server IP address: 192.168.1.1
Relay agent IP address: 0.0.0.0
Client MAC address: TRENDnet_ed:73:32 (3c:8c:f8:ed:73:32)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (53) DHCP Message Type (ACK)
Length: 1
DHCP: ACK (5)
Option: (54) DHCP Server Identifier (192.168.1.1)
Length: 4
DHCP Server Identifier: 192.168.1.1
Option: (51) IP Address Lease Time
Length: 4
IP Address Lease Time: (100000s) 1 day, 3 hours, 46 minutes, 40 seconds
Option: (58) Renewal Time Value
Length: 4
Renewal Time Value: (45269s) 12 hours, 34 minutes, 29 seconds
Option: (59) Rebinding Time Value
Length: 4
Rebinding Time Value: (82769s) 22 hours, 59 minutes, 29 seconds
Option: (1) Subnet Mask (255.255.255.0)
Length: 4
Subnet Mask: 255.255.255.0
Option: (28) Broadcast Address (192.168.1.255)
Length: 4
Broadcast Address: 192.168.1.255
Option: (3) Router
Length: 4
Router: 192.168.1.1
Option: (15) Domain Name
Length: 3
Domain Name: lan
Option: (81) Client Fully Qualified Domain Name
Length: 18
Flags: 0x03, Server overrides, Server
A-RR result: 255
PTR-RR result: 255
Client name: KowloonTong.lan
Option: (6) Domain Name Server
Length: 16
Domain Name Server: 208.67.220.220
Domain Name Server: 8.26.56.26
Domain Name Server: 91.239.100.100
Domain Name Server: 192.168.1.1
Option: (255) End
Option End: 255