I don’t understand why there is so much confusion here.
This has nothing to do with Firebase, there are like 5 total proprietary libraries being pulled in here, which can and do work regardless of using FCM or if GMS is available on the system.
We know this is the case because their ads library and crash reporting library both work regardless of GMS on system.
Signal for Android with these libraries as is, is not and has not been FOSS since the beginning.
That is it.
That is why it is listed on a website called “isitreallyfoss.com”.
I swear I’ve had this exact conversation at least a dozen times over the years.
You can’t say it is FOSS, as long as it has proprietary libraries: it is not FOSS.
I really don’t care to discuss this any further.
I’ve made the facts clear and Signal has bigger issues such as being a silo or relying on phone numbers or lack of true multi-device support, which is why I’ve never recommended it.