Avatars Guides
Creating Avatars with VRM Assets | Mona
Using ‘VRM for Blender’ for Rigging | Mona
Blender A-pose to T-pose
Another way as suggested in Discord/showcase
Once rigged select your skeleton/armature and then enter into pose mode. Move the arms up until they are out strait in a t pose. Then in your VRM Operator setting change T-Pose from Rest Position to Current Pose and export