Hello,

I am from UBports, the team behind the community-based development of 
Ubuntu Touch, the mobile OS that was once developed by Canonical and is 
now getting more and more traction again. Just to add our experiences 
with Signal:

- There was an unofficial Signal App for our phone called Textsecure and 
it worked basically, however it had a lot of problems and we wanted to 
fix them in order to allow our users also to have a Signal client 
available

- We quickly learned how Openwhisper is not interested in having another 
client on a foreign ecosystem like ours: While our codebase would be 
open-source and also open for review, questions were just ignored. There 
is also no developer community page or forum or something technical. You 
can only write to the general support.

- When we asked if Signal was able to send push notifications to our 
servers, again we were delayed and ignored. But whats Signal without 
push? You are not going to check the App all day long.

- Most of our users are on Telegram: We got active support by the devs, 
we got push notifications and we do not feel rejected. Also Matrix is 
first class citizen on our phones.

So my recommendation is just to ignore Signal, as they ignore us. It´s 
sad but true, even when things are open-source, it means nothing if the 
parties cannot collaborate on it.

Cheers Florian