Gallery

• https://f-droid.org/packages/org.fossify.gallery/

File Manager

• https://apt.izzysoft.de/fdroid/index/apk/org.fossify.filemanager

Calander

• https://apt.izzysoft.de/fdroid/index/apk/org.fossify.calendar

Note: I use droid-ify, another client for Fdroid, but personally prefer this one as I can easily add other necessary repositories that add even more apps to the store front. Droid-ify