GWA2 has a watch always on feature. You can access it from Quick Setting menu. But it doesn’t keep the screen on during workouts (Running, Walking …). The watch would return clock screen after a while.
I accidentally find out how to get screen always on for activities.
First you need to access to Workout feature, (list of all workouts on the watch).
On home screen swipe right (watch screen to the right not your finger) , until Add widget button and choose that one.
On widget list, find Work out widget and add then go back to Widget list, open Work out.
On Activity list choose the … dot for settings of the activity.
You can see Screen always on feature in that menu.
For my watch (44mm) it would take about 60% battery for 2 hours running.
say Linux! 