I share a very simple but useful GeoNode my Magic-UV UnWrap, to do UV mapping, and if you export the file in glTF format the UVmap is perfect, this is the tool everyone was looking for, and I'll give you for free, what more do you want?
In the video I add a Vertex Group with the same name of my Named Attribute and then I start assigning to that group some vertexes as the Seam Attribute for UV Unwrap node.