If you can't ensure a working network connection and DNS infrastructure between several networks, you might opt for LsPush. This is a small executable which scans Windows computers and sends the result back to your Lansweeper server using direct server connection (port 9524/TCP by default), file share or mail. You can find details in
this KB article. It is possible to configure a scheduled task for running LsPush and deploy it via group policy.
In order to agentless scan foreign domains without domain trust, you'll need to add the correct DNS server and DNS suffixes to your Lansweeper server's network settings, as described
here. Certain
ports need to be open as well. With LsPush you don't need all this.
LsClient is the only scanning method available in the freeware version of Lansweeper. Technically it equals the agentless scanning methods, as your Lansweeper server will be scanning the target computers.