Samsung X5 as boot disk? (no GUID selection, no APFS selection)

Contact Samsung tech support for help. That is not an Apple product.

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Thank you for your understanding and support.

I am using a Samsung X5 with Mojave installed right now. It was wise not to use the Samsung Portable SSD Software and not setting an encryption password. Setting a password has caused a lot of problems for people.

It is easy to properly format your X5 using Disk Utility. Open Disk Utility. As was already mentioned, select "View", "Show All Devices". Select the "Samsung Portable SSD X5 Media", in the Disk Utility sidebar, not the volume below . Then click on "Erase" in the top tool bar. In the dropdown select Scheme: GUID Partition Map, then Format: APFS. Click on the "Erase" button at the bottom right of the dropdown. Let Disk Utility finish the process. If you wish to make more partitions you will now be able to use the "Partition" button.

Now you are ready to install Mojave on the X5. Open the Mojave installer and select it as the destination.

In Disk Utility, do you have View (top-left of window) set to "Show All Devices"?

Then you should be able to select the SSD drive all the way at the left and Erase with Partition options.