Signal Server has not seen updates for over 9 months. Moxie openly states that is not part of Signal's core values to support federation in the network.
IOW, even though they say they don't want to control your conversation, they do want you in their hands.
Why does any source code exist then? What is the point of GitHub with codebases that are 7+ years old? Would mass adoption of the outdated server force updates or god forbid a fork of the code base?
Please excuse me for being direct, I do not accept your defeatist attitude on this one. You won’t have stickers, such a shame, but you would have the ability to create your own signal service
If Signal was the only alternative to have an internal messaging tool, sure, it would make sense to invest time and money on it to keep it up.
But it doesn't. There are options. If I had to choose, I would rather invest this time and money to collaborate on the existing protocols that do have the goal of being fully open. Matrix and XMPP can do the things that I want and there are plenty of people working on them to overcome the present issues and challenges for mass adoption.
Why should I swim upstream by myself if there is no special reward for this kind of effort?
Moxie is not friendly towards such third party clients that connect to the main network. Also, I only used it as an example. There might be other reasons for a ban. The point is that you don't depend on them.
IOW, even though they say they don't want to control your conversation, they do want you in their hands.