As Kodi is called with sudo -u osmc environment variables are not retained and as a result not available in Kodi.

The easiest way I have found to set environment variables like for example no_proxy is to add them to /etc/environment and then configure sudo to include /etc/environment on every invocation.

You need SSH access to the device

ssh osmc@device

sudo sh -c 'echo "Defaults        env_file=/etc/environment" > /etc/sudoers.d/osmc-environment'
echo "no_proxy=nas" >> /etc/environment

systemctl restart mediacenter