ExFed

Following that logic:

Many popular Linux distros contain closed source blobs. Ergo Linux is closed source.

Not open source

There are lots of good reasons to be upset with how Signal produces builds. And maybe Signal has no good reason why they keep opaque dependencies. But by every common definition of the term, Signal is open source. Being on FDroid is not the definition of open source.

Please don’t gatekeep. There are better ways to criticize Signal. This is not one of them.