Also polyfill buffer and process/browser

webpack.config.js

@@ -250,6 +250,10 @@ module.exports = (env, argv) => {
 
                 // Polyfill needed by counterpart
                 util: require.resolve("util/"),
+                // Polyfill needed by matrix-js-sdk/src/crypto
+                buffer: require.resolve("buffer/"),
+                // Polyfill needed by sentry
+                "process/browser": require.resolve("process/browser")
             }
         },
 
@@ -721,8 +725,8 @@ module.exports = (env, argv) => {
 
             new webpack.EnvironmentPlugin(["VERSION"]),
 
-            // Automatically load buffer & process modules. Webpack 5 doesn't polyfill them
-            // automatically anymore.
+            // Automatically load buffer & process modules as we use them without explicitly
+            // importing them.
             new webpack.ProvidePlugin({
                 Buffer: ['buffer', 'Buffer'],
                 process: 'process/browser',