In case you still need it (and use Sharepoint from Azure)

If you're using Azure instance, You can configure an App in a Sharepoint Site, with Permission to read and write files or lists. Here's some resources on how to connect to the REST API. (Thank you Vikram Samal!). It is a very easy-to-understand guide.

part 1: https://vikramsamal.medium.com/how-to-test-sharepoint-office-365-online-rest-api-crud-operation-using-postman-client-1895b871603b part 2: https://vikramsamal.medium.com/how-to-connect-and-test-sharepoint-office-365-online-rest-api-crud-operation-using-postman-client-6de83d502c41

With that configured, you can design two transformations, one to get the token, other to upload a file using the token. Example: Basic design of Job to Upload CSV File to Sharepoint

1 - Get Access Token

• Read tenant, app and secret info from file
• Make HTTP POST Request to get Access Token
• Move "Bearer {access token}" to the result

2 - Upload File Sharepoint

• Load file content into memory
• Upload file using REST Client POST method
• Get result code 200 to make sure it was uploaded