Kali just came with their " Kali NetHunter App Store" (which does appear to be a copy of both the F-Droid landing page & app) & the repository is:
https://store.nethunter.com/repo
Source: Kali NetHunter App Store
EDIT: Didn’t realize I’d have rights to edit that first post, so I have added the NetHunter repo into the list.