is it possible to upload a file to the File Cabinet over sftp or similar? without having to have a login to netsuite

yes https://netsuite.custhelp.com/app/answers/detail/a_id/51361

that seems the wrong way around. i want to initiate the upload from outside of netsuite, and upload to a location that ns can access

you can have a suitelet URL which your app pings and calls the above

@JBL Would something like this help? https://timdietrich.me/blog/netsuite-file-cabinet-suitescript-suiteql-restlet/