Missing GL_ES_VERSION_3_0 guard for GL_TEXTURE_CUBE_MAP_SEAMLESS in GL_ES_VERSION_3_0 in vtkDGOpenGLRenderer.cxx
GL_TEXTURE_CUBE_MAP_SEAMLESS is not a valid constant for GLES - GLES 2.0 does not support seamless textures, and for GLES 3.x it is always on, see https://registry.khronos.org/OpenGL/specs/es/3.2/es_spec_3.2.pdf#section.G.2
This only affects the 9.3 branch (AFAICS), the relevant code was removed in master with 9adc1ed8
Also see:
!5758 (comment 598567)
!6446 (comment 694923)