One candidate is https://github.com/russhwolf/multiplatform-settings. Particularly, the no-arg release greatly simplifies the setup. But it doesn't include Windows out-of-the-box (painful, but solvable) and the library lacks support for Linux (more problematic, draft PR in https://github.com/russhwolf/multiplatform-settings/pull/54).
One candidate is https://github.com/russhwolf/multiplatform-settings. Particularly, the no-arg release greatly simplifies the setup. But it doesn't include Windows out-of-the-box (painful, but solvable) and the library lacks support for Linux (more problematic, draft PR in russhwolf/multiplatform-settings#54).