Since this question just popped up in the HZ support forum, I thought I'd do a quick screenshot based tutorial on how to install the F-Droid app store on Android phones and tablets.

This was done with a fresh installation of LineageOS 15.1 on a Nexus 5X. The same principal applies to LineageOS 16. This corresponds to Android 8 and 9. Remember, it might look very different on your phone if you're running the stock version of Android which came with your phone, but in general, the process is the same everywhere.

Open your preferred browser and navigate to f-droid.org:



If this is a fresh install, you're gonna have to allow file access:



The next question, I think, only pops up because you're downloading a file of a type that could cause harm. For reference, if you're a Windows user, this is like a warning before you download .exe files. Tap download:



Open your file manager.



Navigate to Download:



Tap the APK file you just downloaded:



You will get a security warning:



In this case, this is perfectly alright. Tap "Continue". Now you can install F-Droid:





After you start it for the first time, it will update the repositories:



Patience, my young Padawan.

When it's done, you will see a list of recently updated apps, and a green search icon at the bottom. Tap the search button to find the app you want. This being Hubzilla, I'm using Nomad as my example.





Tap "Install". Starting with Android 8, you have to allow third-party sources individually, so it will ask you if you want to allow F-Droid to install "unknown apps". Tap settings in the following screen:



Then turn on "Allow from this source":



After you hit the back button, it will let you tap install:



Now the "Install" button on the Nomad page will be replaced with "Uninstall" and "Open":



That's it, you're done. Now you can access Nomad just like any app install from the Play Store: