Forum Thread: 3 Different Ways - Check Treble Support for Your Phone

This is only for those if their your phone has been updated to Android 8.0 Oreo or higher.

Phones pre-installed with android Oreo are required to support Project Treble — but that isn't the case if your phone gets updated to Oreo. Some OEMs are adding Treble support, others are not. But you can see if your phone got it by using the methods in the video, then your phone supports Treble

Treble will help speed up Android updates in the future by separating the OS from the vendor-specific aspects of your firmware. I hope your phone returns that "true".