Operating system: Ubuntu 18.04
Graphics card: Radeon RX 580
Short description of error
An issue with both Cycles and EEVEE in Blender 2.8 beta. Whenever a .png image with transparency is used, Blender hides RGB channels instead of Alpha channel. UV editor seems to show transparency right, so the issue is in viewport and on rendered images.
Exact steps for others to reproduce the error
Render with Cycles or EEVEE