Do not edit /etc/resolv.conf. It will likely be replaced by NetworkManager.

Open a shell and add nameserver for existing connection.

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nmcli con mod $ssid ipv4.dns "1.1.1.1 1.0.0.1"

The SSID can be found with nmcli con.

Replace the IP addresses to your desired ones.

Now restart the connection to apply the changes.

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nmcli con down $ssid
nmcli con up $ssid

Verify with cat /etc/resolv.conf.