The best alternatives to Kanso are Simply Learn Japanese, LanGo, and Mainichi. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Kanso?
AssemblyAIβ Speech-to-Text API with superhuman accuracy
Rethinking language learning. LingoTime is a new app to learn Japanese vocabulary and kanji on all Apple platforms from watchOS to iOS and macOS. Unique features likes widgets, iCloud sync, Smart SRS support your journey, wherever you are.
I created Kana Trainer because I couldn't find an easy and not bloated app to learn Japanese Kanas. I mixed Machine Learning with some algorithm and a simple interface. If you're new to Japanese language, this app will be of great help.