Fix is now merged.
Don't hesitate to contact us if you still have any issue

More than a week without any answer from the user.
Closing for now.

Can you please follow submission template, and provide a .blend with these 3 cubes, and the resuting .gltf / .glb file

I not agree with the analysis.
Factor of the mixShader node will do the following : 1 for transparent, 0 for opaque.
The Add node is used as factor. So if you have an alpha of 0.2, you have to set factor to 0.8.
The second image is wrong, because add 0.8 and 0.2 --> full transparent because of factor of 1.0

This is now fixed in 5fdd91c09edf7c5a4794a3de4fbb1a7603d609f0

Discussion will take place in upstream issue tracker:
https://github.com/KhronosGroup/glTF-Blender-IO/issues/424

This will be manage on upstream issue tracker:
https://github.com/KhronosGroup/glTF-Blender-IO/issues/419

This issue will be manage on upstream issue tracker:
https://github.com/KhronosGroup/glTF-Blender-IO/issues/420

This is now solved after recent commits

This bug is now fixed after recent commits

Can you please try with a more recent build.
This should already been fixed few days ago.

No news, closing.
Don't hesitate to reopen if error is still there

This issue tracker accepts only bugs from official builds (official release or from builder.blender.org).
For any building issue, please ask on IRC #blendercoders on freenode

Upstream issue will be managed here : https://github.com/KhronosGroup/glTF-Blender-IO/issues/385

Should be fixed now

This is not a bug, you have to increase the clipping end of the 3D view

In Pose mode + Weight Painting, selection of bones is now on CTRL + LMB,
but how to select multiple bones ? Seems SHIFT + CTRL + LMB doesn't work

Seems this is a perfect duplicate of T62343, closing

Committed

@Ed Mackey (emackey) Should be OK now

@Ed Mackey (emackey) Ok, I will check it