Export armature DAE -> glTF rotates mesh 90 degrees To reproduce:

Download DAE
Open in Blender
Export to glTF (default settings)
Open exported glTF in Blender
Click on mesh
Go into edit mode
See that it is rotated 90 degrees around the X axis
The solution was to upgrade Blender from 2.82. 2.83 had big improvements in skinning for the glTF importer.
By the way, if you ever have issues with how a skinned mesh looks in edit mode, you can also try toggling the &quot;Guess Original Bind Pose&quot; option on the glTF import screen.