CM13 on Nexus 9: Any app that internally opens a webpage or otherwise uses System WebView crashes
The internal graphics driver was out of date. Updating the vendor image solved the problem. Updating also fixed a non-working camera.
CyanogenMod ROMs do not provide updated device-specific drivers (&quot;vendor&quot;), baseband firmware (&quot;radio&quot;; for cellular devices only), or bootloaders. These are stored on their own partitions and must be flashed manually at the fastboot bootloader. To do so, download the latest stock system image, extract it, and flash the applicable files:
fastboot flash bootloader &lt;bootloader-image&gt;
fastboot flash vendor &lt;vendor-image&gt;
fastboot flash radio &lt;radio-image&gt;


Update: An official CyanogenMod blog post states:

Nexus devices now ship with a large portion of their proprietary code in a vendor partition on the device itself. This is not something CM’s installation will update for you. If your vendor partition doesn’t match with the CM build, you will be met with an error on boot up that the system is potentially corrupted. To prevent this message (and ensure things like camera function), you should make sure you are on the latest available vendor image for your device. Vendor images can be found in the stock Nexus factory images provided by Google here. Extract the latest available zip and flash the vendor image through your bootloader with ‘fastboot flash vendor vendor.img’.

The error at boot-up looks like this:

Android System
There's an internal problem with your device. Contact your manufacturer for details.