Set `ESNext` as the value for `module` under `compilerOptions` in your TSConfig will output an ES module every time. What it doesn't support currently is changing the output file extension, if thats what you meant
Right, I remember now. The file extensions weren't correct, but even after renaming the files it does not work because the imports were also missing the correct file extension (which is mandatory in ESM mode in Node.JS). At that point I gave up.