My initial thought would be that these assets have port 135 TCP open, which for Lansweeper means it is a Windows asset.
To see what ports are open you can do a test with devicetester.exe, which can be found in Program Files (x86)\Lansweeper\Actions on your Lansweeper server. Perform the test from your Lansweeper server to the problem machine, submit any relevant (SNMP or SSH) credentials.