Windows 7,8.x and 10: https://download.nextcloud.com/desktop/releases/Windows/Nextcloud-2.3.3.1-setup.exe
Mac OSX 10.10+, 64 bit: https://download.nextcloud.com/desktop/releases/Mac/Installer/Nextcloud-2.3.3.84.pkg
Linux Applmage: https://download.nextcloud.com/desktop/releases/Linux/Nextcloud-2.3.3-x86_64.AppImage
Android Google Play Store: https://play.google.com/store/apps/details?id=com.nextcloud.client
Android F-Droid: https://f-droid.org/packages/com.nextcloud.client/
Mac App Store: https://itunes.apple.com/us/app/nextcloud/id1125420102?mt=8
Windows Store: https://www.microsoft.com/store/apps/9nblggh532xq
Other Resources:
- DAVDroid supports Nextcloud Calendar, Tasks and Contacts, syncing your agenda, tasks and addressbook (android only, open source)
- Find iOS Sources here, Android Sources here, direct APK download here and Windows Mobile sources here.