Firefox keeps redirecting to modem home gateway page.

Windows 10.
I have a mobile modem (http://192.168.8.1) and when typing some URL's in Firefox's adress bar I'm getting redirected to the above mentioned URL (the modem's setup page.)
If there's a site I've never been to before this happens every time, and also for some frequently visited sites.
By typing in the URL a second time redirection won't happen.
What is the cause of this behaviour, and how do I stop it?

/flushdns in a cmd window

Samuria said:

Open CMD prompt type

Ipconfig /all

Post results if the DNS is set to the modem set DNS to 1.1.1.1 & 8.8.8.8

Microsoft Windows [Version 10.0.19045.3208]

C:\Users\emtor>Ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : LAPTOP-R5K34KMR
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Wireless LAN adapter Connection to lokal network* 1:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter
Physical Address. . . . . . . . . : 70-CF-49-51-62-4D
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Wireless LAN adapter Connection to lokal network* 2:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Wi-Fi Direct Virtual Adapter #2
Physical Address. . . . . . . . . : 72-CF-49-51-62-4C
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes

Wireless LAN adapter Wi-Fi:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Intel(R) Wi-Fi 6 AX201 160MHz
Physical Address. . . . . . . . . : 70-CF-49-51-62-4C
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : fd3c:cd5d:b0e3:2900:b93b:5c7e:2153:57fc(Preferred)
Temporary IPv6 Address. . . . . . : fd3c:cd5d:b0e3:2900:8108:a345:d485:e907(Preferred)
Link-local IPv6 Address . . . . . : fe80::c8d7:2983:3389:3467%5(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.8.108(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : den 21 juli 2023 19:32:18
Lease Expires . . . . . . . . . . : den 25 juli 2023 14:32:17
Default Gateway . . . . . . . . . : 192.168.8.1
DHCP Server . . . . . . . . . . . : 192.168.8.1
DHCPv6 IAID . . . . . . . . . . . : 74501961
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-28-5A-B0-3A-00-6F-00-01-46-31
DNS Servers . . . . . . . . . . . : 192.168.8.1
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. . . . . . . . . : 70-CF-49-51-62-50
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes

Make and model of the modem?

Also, try this:

Go into your network adapter in Windows and change the DNS IPs to something like 208.67.222.222 and 208.67.220.220 or 1.1.1.1

The first two IPs are for the free OneDNS service. The third (1.1.1.1) is one of Cloudflare's DNS.

Cloudflare

Home Internet Security | OpenDNS

How to Change Your DNS Server on Windows 10

Thanks all of you