PostActiv
PostActiv is a fork of GNU Social which includes some extra fixes and optimisations to improve performance. It federates just like GNU Social does and so whether you choose GNU Social or PostActiv is really just down to personal prefernce.
Installation
Log into your system with:
ssh myusername@mydomain -p 2222
Using cursor keys, space bar and Enter key select Administrator controls and type in your password.
Select Add/Remove Apps then postactiv. You will then be asked for a domain name and if you are using FreeDNS also the code for the domain which can be found under Dynamic DNS on the FreeDNS site (the random string from "quick cron example" which appears after update.php? and before >>). For more details on obtaining a domain and making it accessible via dynamic DNS see the FAQ. Typically the domain name you use will be a subdomain, such as code.mydomainname.net. It will need to be a domain which you have bought somewhere and own and not one of the FreeDNS subdomains, otherwise you won't be able to get a SSL/TLS certificate for it.
After the install has completed go to Security settings and select Create a new Let's Encrypt certificate and enter the domain name that you are using for PostActiv. If you're using the "onion only" version of the system then you don't need to do this. If the certificate is obtained successfully then you will see a congratulations message.
Initial setup
If you have just obtained a Lets Encrypt certificate as above then go to About on the administrator control panel and you should see your Postactiv domain listed there along with an onion address. You can then navigate to your site in a browser.
To see the login password for your site go to Passwords on the Administrator control panel and select the appropriate username and app. The passwords will be different for each user and may not be the same as the password which you used to originally ssh into the system.
Navigate to your PostActiv domain name and log in.
Blocking controls
The biggest hazard with PostActiv is that it's part of a public federated communications system. This means that conversations and replies from other servers may end up in your "whole known network" stream. The internet being what it is, some of these could be undesirable. You can block individual users or entire domains by going to the Administrator control panel and selecting Domain and user blocking, then adding or removing entries. This blocks domains at the firewall level and also at the level of database and file storage.
If you want to block a particular user then select Block a domain or user and enter the user in the format username@domaintoblock (similar to an email address).