To enable the BigInt in React as of now you have to add this comment to your code:

/* global BigInt */

Please, refer to this.

BigInt is enabled in node_modules/typescript/lib/lib.es2020.bigint.d.ts, so it is part of es2020 not part of esnext.

However, it seems that the ***n lexical expression is not part of lib.es2020.bigint.d.ts. Indeed, that is enabled by esnext.

To enable typescript use with BigInt but without ****n lexical expressions, this configuration worked:

{
  "compilerOptions": {
    "lib": [
      "es2020"
    ],
    "module": "commonjs",
    "target": "es2020",
}

Adding "esnext" to the libs:

{
  "compilerOptions": {
    "lib": [
      "es2020", "esnext"
    ],
    "module": "commonjs",
    "target": "es2020",
}

then enables(*) the ability to '****n' lexical expressions.

(*) Another separate issue is that VSCode (if you are working with that) will sometimes opaquely enable '****n' as a valid expression, even when 'esnext' is never explicitly mentioned in the relevant tsconfig.json file. Perhaps it is enabling esnext implicitly? That behavior is actually not helpful when trying to figure exactly what settings enable the ***n lexical expressions - after adding esnext to a tsconfig file and then removing it, the abilty to use ****n expressions continued anyway.