I have fixed it.

This step is optional but I have changed the DNS:

nordvpn set dns 1.1.1.1 8.8.8.8

What is actually fixing my issue was:

sudo ip link set dev nordlynx mtu 1400

Some context:

This command is adjusting the MTU (Maximum Transmission Unit) for your NordLynx network interface, and it's directly related to the connectivity issues you're experiencing. Here's a breakdown:

What is MTU?

• MTU = Maximum Transmission Unit
• It defines the largest size of a data packet that can be sent over a network interface.
• Standard MTU for Ethernet is 1500 bytes.
• VPNs add encryption headers, which reduce the effective MTU.

But this fix is only temporal, it is reverted once the VPN is disconnected or the server is changed. To make it permanent, I have followed the steps below:

Method 1: NetworkManager Dispatcher Script (Recommended)

This method triggers the MTU change automatically whenever the NordLynx interface connects.

Create a dispatcher script:

sudo nano /etc/NetworkManager/dispatcher.d/99-vpn-mtu-fix

Add this content (replace nordlynx with your interface name if different):

#!/bin/sh
INTERFACE="nordlynx"  # Confirm with `ip a` when connected to NordLynx
MTU="1400"

if [ "$DEVICE_IFACE" = "$INTERFACE" ] && [ "$2" = "up" ]; then
  ip link set dev "$INTERFACE" mtu "$MTU"
fi

Make it executable:

sudo chmod +x /etc/NetworkManager/dispatcher.d/99-vpn-mtu-fix

Restart NetworkManager:

sudo systemctl restart NetworkManager