If you change your PNG images to JPG, then you need to edit the readable glTF file and change the necessary PNG references to JPG before you package the glTF into a GLB. It's best to keep your file size to 4 MB or smaller.
This reduces the total file size, and smaller file sizes allow for quicker download speeds and smoother interactions. Consider compressing the texture files and converting any textures that don't need an alpha channel to a JPG. When using the glTF PBR Metal Roughness configuration, Substance Painter exports texture files only in PNG format.
When you have exported the model, you should have the following files: Use 1024 x 1024 px where possible to reduce the total file size significantly. Usually textures don't need to be larger than 2048 x 2048 px.
If you see more than one texture set, then one of the following was wrong when the mesh was exported from Blender: When you import the FBX file into Substance Painter, you should see only one texture set: In the Texture set settings panel, click Bake Mesh Maps. Add this channel if your model has components that will be transparent. Add this channel if your model has components that will emit light. In the Texture set settings panel, click the + button to add channels: If you see more than one texture set, then see Multiple texture sets. Verify that you correctly exported your mesh by checking that there's only one texture set in the Texture set list panel. Select the FBX file that you exported from Blender, and then click Open.In the New project dialog, click Select to choose a mesh.Create a new Substance Painter project by clicking File > New.Import and prepare the FBX file in Substance Painter Make sure that you use the following export settings:.Enter the path to where you want to export the file.Click the + button to add a new material slot:.