One of the ways of shutting down OSMC besides using the yatse remote is to use curl along with json rpc to shut down the raspberry pi.

If you try the http get like the below, it will fail

curl http://192.168.1.125/jsonrpc?request={"jsonrpc":"2.0","method":"System.Shutdown"}

You would instead need to encode the url like the below.

curl http://192.168.1.125/jsonrpc?request=%7B%22jsonrpc%22%3A%222.0%22%2C%22method%22%3A%22System.Shutdown%22%7D

Of course you also need to ensure that the port is correct and http is enabled for your OSMC. in my case the port was 80 so that was not a problem.