gfx.waitforpresent consistantly at >150ms in empty scene despite vsync disabled

I have the common problem of low FPS even in empty projects. Profiler says the usual gfx.waitrForPresent indicating a delay on the GPU side. However, its not spikes, but a consistent load of more than 100ms making the applications almost unusable. vSync should be deactivated. Whatever the GPU is doing, my card does not support Profiling so I cant figure out what takes so long. It gets worse if I add a couple of cubes.
Any ideas? I read so far about deavtivating vSync, deactivating graphics jobs (experimental mode), and tried different built targets without success.

OS: MacOS Mojave 10.14.4, Built: Editor / WebGL
Unity Version: 2018.3.6f1

Any ideas are highly appreciated as we can’t ship our product right now because of it.

Very familiar for me

A clean unity install and switching the project to 2019.1.4f1 fixed it for me.
I am now under 2ms for three cubes on my MacBook.