To match the route you want to add via the command:

bash
Copy
sudo ip route add 10.1.28.0/24 dev tun0

in the GNOME VPN Route settings:

Step-by-step instructions:

1. Address: Enter 10.1.28.0/24 in the Address field. This specifies the network and subnet mask.

2. Netmask: Leave this field empty or set it to 255.255.255.0 (which corresponds to /24). The GNOME VPN interface usually infers the netmask from the CIDR notation, so you may not need to fill this in.

3. Gateway: Leave this field empty. The dev tun0 part of your command specifies that the route should use the tun0 interface directly, not a gateway.

4. Metric: Leave this field empty unless you have a specific reason to set a metric. The default metric will be used if you leave it blank.

5. Use this connection only for resources on its network: Check this box if you want to ensure that only traffic for the 10.1.28.0/24 network uses this VPN connection.

Summary Table:

This setup will ensure that traffic for the 10.1.28.0/24 network is routed through the VPN interface, just like your ip route add command.