The new Oxygen OS 5.1.5 update sent out to the OnePlus 5 and 5T has finally granted the devices their very own Treble powers. The update weighs is a heavy 1.69 GB download and will be rolled out gradually.
https://www.notebookcheck.net/OnePlus-finally-brings-Treble-support-to-the-OnePlus-5-and-OnePlus-5T.324056.0.html