Repro steps:
1. Downlaod this project
2. Load it up in Unity Editor 2019.1.0a11
3. Open Package Manager Window and notice that you can't read any of the letters
4. Notice this only happen for this window -Player Settings, for example, works just fine.

Cannot repro in 2018.3.0f2 or 2019.1.0a10

reproduced in 2019.1.0a11 and 2019.1.0a12

Note: the project does use LWRP , but even after removing LWRP completely, i still can't get Package manager to render normally.
The only workaround is to change the graphics API.

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HLSLcc emits "switch" when compiling to GLSL ES2. This is a reserved keyword and produces a compile-time error.