Newdle implements Enter to Submit in an incompatible-with-Safari-and-Japanese-text-input way. Please consider implementing a mitigation.
See https://ef81sp.github.io/ime-vs-input-keyboard-shortcut/, https://kai-rin.github.io/your-form-submits-mid-japanese-input/ and https://dninomiya.github.io/form-guide/stop-enter-submit for the background and mitigation.