Allowing automatic fallback to WebGL backed by the software renderer SwiftShader is deprecated and WebGL context creation will fail instead of falling back to SwiftShader. This was done for two primary reasons: 1. SwiftShader is a high security risk due to JIT-ed code running in Chromium's GPU process. 2. Users have a poor experience when falling back from a high-performance GPU-backed WebGL to a CPU-backed implementation. Users have no control over this behavior and it is difficult to describe in bug reports. SwiftShader is a useful tool for web developers to test their sites on systems that are headless or do not have a supported GPU. This use case will still be supported by opting in but is not intended for running untrusted content. To opt-in to lower security guarantees and allow SwiftShader for WebGL, run the chrome executable with the --enable-unsafe-swiftshader command-line switch. During the deprecation period, a warning will appear in the javascript console when a WebGL context is created and backed with SwiftShader. Passing --enable-unsafe-swiftshader will remove this warning message. Chromium and other browsers do not guarantee WebGL availability. Please test and handle WebGL context creation failure and fall back to other web APIs such as Canvas2D or an appropriate message to the user.
https://chromium.googlesource.com/chromium/src/+/main/docs/gpu/swiftshader.md#automatic-swiftshader-webgl-fallback-is-deprecated