Unity 2019 + Standalone Mac + OpenGLCore extremely poor performance

I made a simple scene with just a plane and a cube.

It lags extremely (like 3 FPS) when running on the OpenGLCore Graphics API, while it runs smoothly with the Metal API.

I have to use the OpenGLCore Graphics API, however, for third party library compatibility (the full context is that I'm trying to upgrade my existing project from Unity 5 to Unity 2019).

What's interesting is that my existing project on Unity 5 also uses the OpenGLCore Graphics API, and it runs perfectly smoothly.

So it seems like an issue only when using both Unity 2019 and the OpenGLCore Graphics API on Mac.

Aside from that, everything runs perfectly on Windows.

What can I do to workaround this issue? It's not an option for me to use the Metal API, because I have years of work built on my UI plugin (Coherent GT) which relies on OpenGL API.