Zooming Scene view with holding alt and right-click is not working also on holding alt with left-click camera is not getting orbited around the current pivot point in the Scene View

Steps to repro:
1. Create a new project.
2. Switch to the Scene view
3. Hold Alt, and left-click and drag in the Scene view
4. Hold Alt, and right-click and drag in the Scene view

Actual Result:
Scene View is not getting zoomed on holding Alt and right-click and Camera is not orbited around the current pivot point on holding Alt and left-click

Expected Result:
Scene View is zoomed and Camera is orbited around the current pivot point on holding Alt with left-click and right-click.

Reproducible in: 2019.3.0b1, 2019.2.1f1, 2019.1.0f2, 2018.3.0f2

Environment:
Occurs only on Linux (ubuntu 16.04 LTS)