It’s good that you found a way!
You should avoid accessing private variables, though, as they might be renamed/deleted in future versions. Instead, you can do: mesh.isUndexed = true;
The default WebGPU limits are quite low (see WebGPU) but you can request higher limits by filling in the deviceDescriptor property of the options parameter you pass to the constructor.
To simplify things, we’ve added the setMaximumLimits property to the option object, which will set the maximum limits supported by your browser/GPU (there’s also the enableAllFeatures property which will enable all extensions supported by your browser/GPU). The playground is to set both properties to true.
Note that Chrome does not yet implement all limits correctly (for example, Chrome says 60 for maxInterStageShaderComponents but my GPU supports more).