You can make the changes to the interfaces and default gateway and DNS in the USS Gateway UI. Then to make sure those settings don't overwrite we'll need to make changes to two things via the USS gateway linux console
1. Netplan, this is used to set the IP address of the gateway along with default gateway and DNS. here are the commands to use:
sudo su nano /etc/netplan/00-installer-config.yaml
Edit the yaml file paying attention to the formatting as it's sensitive to that. Below is an example of what the file should look like from my device:
If the Gateway keeps reverting to a different IP address, you can do the following:
Add a line under gateway4 with:
dhcp4: no
This will enforce no DHCP.
Then once you finished press ctrl+x to close and save and Y to confirm changes
then run:
sudo netplan apply
2. Then we need to make sure DNS is set correctly:
nano /etc/systemd/resolved.conf
then make sure the correct DNS servers are included there, please Un-comment the relevant lines by removing the # at the start of each line you edit:
Then once you finished press ctrl+x to close and save and Y to confirm changes
systemctl restart systemd-resolved systemd-resolve --status | grep 'DNS Servers' -A2 (this will show you the changes)