GTrusted

When you first use the Samsung Portable SSD T3 with the LG Google Nexus 5X over USB Type-C, you will see a couple notifications.  

If you select the 'USB for charging' notification, you will be brought to the 'Use USB for' pop up window, where you should keep the selection as 'Power supply' so the Nexus 5X will be providing power to the T3.  

If you select the 'Unsupported Samsung USB drive', will you be brought to a "Format as portable storage' screen.  Just select the notification and proceed to format as a portable storage (which will erase the drive and reformat to MS-DOS (FAT32) which can be read by Android phones, Mac's, and Windows PC's. Be aware that once you do this, all the content in the Samsung drive will be lost.

Since I wanted to keep the content on the Samsung drive to install the security applications for other reviews, I decided not to format the drive.  If you do format the drive, click here to see another similar review for how to format and move files around on the LG Google Nexus 5X to a USB drive.