Operating system: Linux-5.4.0-7642-generic-x86_64-with-debian-bullseye-sid 64 Bits
Graphics card: Quadro RTX 4000 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.100
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-09-21 08:49, hash: rBd72b5785eb02
Worked: 2.91.0 Alpha around September 15th
Short description of error
The improvement done recently as part of the Image Editor refactor, that shows correct alpha values is no longer working.
I made a video about it on September 15th, compiled that same day and it worked fine. But as of recently it no longer works.
Exact steps for others to reproduce the error
The easiest way to test is with EEVEE bloom, attached this simple file I used in the demo video: