[layer8]

This. Using a Compose key [0] covers a vast range of input use cases and is eminently customizable. For Windows there is WinCompose [1]. For macOS there is [2].

[0] https://en.wikipedia.org/wiki/Compose_key

[1] https://github.com/SamHocevar/wincompose

[2] https://github.com/Granitosaurus/macos-compose