What is the output of "ipconfig /all" on the PC (assuming it's windows), are the DNS settings showing the router? Or some other DNS?
Ex. some VPN software will change the DNS settings to point to the VPN providers DNS servers.
Next, did you check if either of the browsers has DoH enabled? In FF those are under "Network Settings | Enable DNS over HTTPS", that box should not be checked. I don't use Edge so can't help with that.
Here it the output trying two different adapters.
thanks
Wireless LAN adapter Wi-Fi:
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : 802.11ac Wireless LAN Card
Physical Address. . . . . . . . . : A0-9D-C1-1E-D4-E7
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::2595:b7a7:63f8:a54f%26(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.98(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Friday, July 9, 2021 12:26:24 AM
Lease Expires . . . . . . . . . . : Saturday, July 10, 2021 12:26:21 AM
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DHCPv6 IAID . . . . . . . . . . . : 446733761
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-28-3F-9E-88-A8-5E-45-53-83-A2
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled
Ethernet adapter Bluetooth Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Bluetooth Device (Personal Area Network)
Physical Address. . . . . . . . . : 00-15-83-F7-20-83
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe GbE Family Controller
Physical Address. . . . . . . . . : A8-5E-45-53-83-A2
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::8056:2c3a:cbf4:cef3%3(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.1.46(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Thursday, July 8, 2021 10:00:45 AM
Lease Expires . . . . . . . . . . : Saturday, July 10, 2021 12:25:59 AM
Default Gateway . . . . . . . . . : 192.168.1.1
DHCP Server . . . . . . . . . . . : 192.168.1.1
DHCPv6 IAID . . . . . . . . . . . : 363355717
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-28-3F-9E-88-A8-5E-45-53-83-A2
DNS Servers . . . . . . . . . . . : 192.168.1.1
NetBIOS over Tcpip. . . . . . . . : Enabled
Ethernet adapter Bluetooth Network Connection:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Bluetooth Device (Personal Area Network)
Physical Address. . . . . . . . . : 00-15-83-F7-20-83
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled