Android - Treble: How do I check if it is enabled on my device?

Works on unrooted devices also

Install Termux and run getprop ro.treble.enabled

It returns true if your device supports and false if it doesn’t

With adb

adb shell getprop ro.treble.enabled

For users not familiar with terminal and such, Treble Check saves some hassle, and on top of that also offers info on whether the device has A/B system partitions (for seamless updates).