https://en.wikipedia.org/wiki/Firebase
Firebase is a platform developed by Google for creating mobile and web applications. It was originally an independent company founded in 2011. In 2014, Google acquired the platform and it is now their flagship offering for app development. History. Firebase evolved from Envolve, a prior startup founded by James Tamplin and Andrew Lee in 2011.
Google Cloud + Firebase. Firebase projects are backed by Google Cloud, letting you scale your app to billions of users. Read more Trusted by the largest apps and games. Development teams around the world—including NPR, Halfbrick, Duolingo, and Venmo—use Firebase to ship their apps.
I can't since I am only a web programmer. Instead, I gather information from valid sources and listen to what other people say.
OP did mention trackers (look in the title of this post). But that title are wrong. So, so wrong. Firebase are not a tracker. I have only stated the fact that Signal uses Google and asked, "what did you expect?"
If I have given any missleading information, I am sorry. I had just woke up when I posted my 2 first replies here. Am more awake now after breakfast ^^
Glad that I scrolled down and found a proper answer :) You're right. Google might track people using Signal this way, but it doesn't mean they have access to information they don't already have.