A variant of (3) that seems close to ideal is to use conditionally defined functions as suggested, that someone else has already written and generously shared,

A variant of (3) that seems close to ideal is to use conditionally defined functions as suggested, that someone else has already written and generously shared, such as portable-snippets [0]. It has a component specifically to offer cross platform builtins with fallback/emulation on plaforms without direct support. [0] https://github.com/nemequ/portable-snippets https://github.com/nemequ/portable-snippets