For Lansweeper to determine that a target is a Windows machine, it requires port 135 TCP to be open. If that port is closed, Lansweeper will try to scan that asset by other methods and might list it as a network device.
You can find the list of ports used by Lansweeper and the network scan requirements in the following knowledge base articles:
https://community.lansweeper.com/t5/requirements/ports-scanned-or-used-by-lansweeper/ta-p/64273
https://community.lansweeper.com/t5/requirements/network-device-scanning-requirements/ta-p/64380
~~~~~~~ (〃 ̄︶ ̄)人( ̄︶ ̄〃) ~~~~~~~
Sweep that LAN, sweep it!