I’ve never used that script, but it looks like that information about --force is coming from its attempt to add the device.
Your LibreNMS server won’t be able to ping the device 192.168.0.249, so the only way to add it is with the force option of device:add. Ideally, get pings working and it will all work.
If you have to force, the script doesn’t look to have a way to let you do that easily. You could lnms device:add -f manually (Adding a device - LibreNMS Docs), or as a last resort perhaps add -f as another argument before the -g in the highlighted bit here and see how it goes: