Before it's unflagged

• Figure out default export interop with transpilers, either adding __esModule to required ESM on our end (module: add __esModule to require()'d ESM #52166), or transpilers update themselves to check the result returned by require():
• conditional exports for module, regardless of whether it's loaded by require or import. Something like module which is recognized by Webpack and Rollup would be good (maybe this doesn't need to block unflagging, but should be done before stablization) module: implement the "module-sync" exports condition #54648
• Move experimental warning to where require() is actually handling a ESM

Before it is promoted to be stable:

• Implement detection module: support ESM detection in the CJS loader #52047
• Some marker to customize the default exports returned by require(esm) module: support 'module.exports' interop export name in require(esm) #54563
• Support module customization hooks doc: add synchronous hooks proposal loaders#198

Nice-to-haves:

• Add API for dumping or inspecting the consolidated CJS and EJS module graph #52180
• Provide some mechanism to conditionally and synchronously import modules (or just builtins) from ESM #52599 (fixed in process: add process.getBuiltinModule(id) #52762)
• Better documentation on how to publish packages in a post-require-esm era/migration guide: https://github.com/nodejs/package-examples

Bug fixes & changes:

• module: disallow CJS <-> ESM edges in a cycle from require(esm) #52264
• module: fix submodules loaded by require() and import() #52487
• module: support ESM detection in the CJS loader #52047
• module: cache synchronous module jobs before linking #52868
• module: add __esModule to require()'d ESM #52166
• module: remove bogus assertion in CJS entrypoint handling with --import #54592
• module: implement the "module-sync" exports condition #54648
• module: check --experimental-require-module separately from detection #55250
• module: include module information in require(esm) warning #55397
• module: trim off internal stack frames for require(esm) warnings #55496
• module: allow ESM that failed to be required to be re-imported #55502
• module: fix error thrown from require(esm) hitting TLA repeatedly #55520
• module: do not warn when require(esm) comes from node_modules #55960
• module: mark evaluation rejection in require(esm) as handled #56122
• module: only emit require(esm) warning under --trace-require-module #56194

Related features that interoperate with require(esm) and need to be considered when being backported together:

• module: unflag detect-module #53619
• module: add --experimental-strip-types #53725

v22.x backport (see a summary of regression analysis in #55217 (comment))

• process: add process.features.require_module #55241
• module: use kNodeModulesRE to detect node_modules #55243
• src: implement IsInsideNodeModules() in C++ #55286
• [v22.x] backport unflagging of --experimental-require-module and related fixes/refactorings #55217

v20.x backport: #56927