Pokemon GO is different from many games because it can encourage walking and outdoor time. The problem starts when events, raids, gifts, and catches turn the whole walk into screen time.
Set a Pokemon GO App Limit in Screen Time and track sessions with Sandflow. Before opening the game, decide the job: one raid, one walk route, one gift check, or one event block.
Keep the game as part of the walk, not the whole point of the walk. If the Sandflow timer shows that you have been staring at the screen longer than planned, pocket the phone and keep moving.