Are the AOSP Email and Calendar apps dead? Are the AOSP Email (com.android.email) and Calendar (com.android.calendar) apps dead?  I cannot find any information on their development, though they appear to have been stuck on version 6.0.1 for some time.  They are still distributed as part of CyanogenMod.
I cannot speak to cyanogen mod, however my understanding is that cyanogen mod has been taken over/morphed into what is now known as the  Lineage OS Distribution here: https://lineageos.org/ perhaps you can get more info there or check on the android open source project here AOSP Platform Email and here.
Regarding how to install them, see here.