LMT 2.9 and also the Beta 3.0 do not work on Android Q Beta 6 for the Pixel 3 XL.
What I encounter is that LMT service will pop up 1 time (pie controls) and then it will not come back again. A toast message saying "LMT Stopped" appears at the bottom of the screen.
If you open the LMT app and configure the activation areas (thickness, length, gravity, etc) you will be able to see the zones you have configured and a toast message saying "LMT Started". This ofcourse works for one pop up of the pie controls and then stops afterwards.
Beta version does not resolve this behavior