I would like to post reply to this question
but I cannot. Not sure why, but I suppose it is because I am newcommer. Can anybody do it for me? Or tell me, what should I do to be able to reply myself?
The reply follows:
The trick is that at least Mesa AMD driver has limitation that when using dual source blending, the used blending function has to be GL_FUNC_ADD or GL_FUNC_SUBTRACT. I do not know how the driver behaves in windows. See this https://gitlab.freedesktop.org/mesa/mesa/-/issues/4183 for details.