Disable IPv6 privacy extensions, disable MAC address randomization and enable 1.1.1.1 DNS with NetworkManager

README.md

Make sure to setup NetworkManager as described in https://wiki.debian.org/NetworkManager first. In particular, be sure to remove the devices you want to manage with NetworkManager from /etc/network/interfaces.

/etc/NetworkManager/NetworkManager.conf should look like the following:

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=true

main.sh

while read i; do
  echo "Setting up connection $i ..."
  sudo nmcli conn modify "$i" ipv6.addr-gen-mode eui64
  sudo nmcli conn modify id "$i" 802-11-wireless.cloned-mac-address permanent # This is only relevant when using Wifi
  sudo nmcli conn modify "$i" ipv4.dns "1.1.1.1"
  sudo nmcli conn modify "$i" ipv6.dns "2606:4700:4700::1111"
  sudo nmcli conn up "$i"
done <<< "$(nmcli -g name conn show)"