Short answer
Yes: Aktar is free on the App Store for iPhone and iPad and on the Microsoft Store for Windows. The Android app is in review on Google Play.
Get the iPhone and iPad app on the App Store and the Windows app on the Microsoft Store. They connect to the same S3-compatible storage, so your existing buckets and links work there too. Follow the getaktar organization on GitHub to hear when Android lands.
On Windows you can also install Aktar-Setup.exe from GitHub instead of the Store: updates arrive the day they're released, but Windows may warn you, since the app isn't signed yet. How to install the .exe.