I know UPBGE doesnt have built-in hardware skinning for bones yet, but is it maybe possible to have a shader skin the skeleton for you rather than through a modifier? I know this could be done through GLSL vertex shaders. Would really love to see a shader that skins armatures to the GPU rather than the CPU.
In order to perform skinning via shader you need the weights of the vertices through attributes, but the only available attribute in BGE/UPBGE is the tangent.
What about Geometry nodes?
On top of the weights, you would need access to the transformation matrix of every bone that influence the current vertex, or in the worst case the matrix of every armature bone and select the matrices by index or name, modulate them by the weight and accumulate them into a final matrix that will be used to transform the vertex’s position, normal and tangent.
I never used geometry nodes, maybe it is possible, but I find it to be unlikely.