Apt
gpg --keyserver hkps://keyserver.ubuntu.com --recv-keys KEY_YOURE_MISSING
gpg --export KEY_YOURE_MISSING | gpg --dearmor -o /usr/share/keyrings/some_name.gpg
deb [signed-by=/usr/share/keyrings/some_name.gpg] http://server.com/ main contrib
deb [trusted=yes] http://server.com/ main contrib
apt-get update --allow-unauthenticated
apt-get update --allow-insecure-repositories