Sometimes as an alternative (for windows devices anyways), when we do not have domain trust, credentials, or anything yet... I will give the lspush.exe standalone executable and have the other company deploy/run the executable and point the output file to a network folder... then they zip the folder, and I take it and drop it in the import folder on a scan server... that way the other side knows that no credentials were shared, and nothing was actually installed on the computer.
Or... again for windows stuff with same scenario, you can have them install the LSAgent and point it to your cloud relay (if allowed) and then define the foreign subnets... but that involves an installation and also the cloud relay might be scrutinized by security, etc. etc.
I prefer to do the standalone .exe because as we all know, you have to fight with ports and permissions when you are pulling data (i.e. having the scanning server scan them) - with lspush.exe, as long as the coverage is 100% deployed/executed, your results should be 100% as well - as I promise you you will be fighting with scanning errors if you just scan from a server...
just my 2 cents.