Unfortunately fixes were made to QQuickOpenGLShaderEffect(Node) during the past 2 years, without porting these to QQuickGenericShaderEffect, which is now also used by the RHI code path. Before 5.14 the "generic" implementation was only in use when one chose to run with the rarely used d3d12 backend of Qt Quick. With the QRhi-based story the generic implementation is the primary (and only) way to back ShaderEffect.
The implentations should be synchronized before removing the OpenGL version. For exampe, port the signalmapper related changes and whatever else got changed. Then verify it all still works.
Once this is done we can remove the OpenGL-specific shadereffect node implementation. This is harder than it looks, and there is also some functionality (UniformAnimator?) that has never been ported to the generic (adaptation layer based) shader effect node...