System Information
Operating system: Linux Mint 19.3 (Ubuntu 18.04.3 based)
Graphics card: GTX 1080

Blender Version
Broken: 2.83.1
Worked: unknown

Short description of error
When using the glTF2.0 exporter to export a model with an alpha value other than one, this value does not seem to get saved.
This is with standard settings (glTF binary, Materials enabled).

Exact steps for others to reproduce the error
Change Alpha for a material to something other than 1
Export with glTF2.0 exporter
Import into Blender and check the Alpha value; Or check in any other application.