MacOS seems to assume a WLAN connection to be free of charge if and only if it is not a tethered iPhone connection. So it will run all background update and maintenance processes via that WLAN connection. As my WLAN is in fact a small box with LTE access (payed by volume) I would like to configure the connection as if it were a tethered mobile connection, which it really is.
The answers to the similiar question Managing Metered Connections on OSX all recommend some third party tools, how can I solve it solely with built-in functionality and tools (macOS Sierra, if it helps)?