2 HiNative alternatives

Google Japanese Input

Typing Japanese on Windows or Mac

BeginnerIntermediateAdvanced

Free

Google's Japanese input method (IME) for typing Japanese on your computer, with accurate kana-to-kanji conversion and suggestions.

LangCorrect

Getting your writing corrected by native speakers

IntermediateAdvanced

Free + paid options

Keep a journal in Japanese and native speakers correct it sentence by sentence, explaining why. In return, you correct entries written in your own native language.