Part of the problem with the obsession with "opsec" is that none of it is actually secure, you're just 1) giving people the false impression that it is and 2) creating the appearance of consciousness of guilt.
Mikhail Gorbaechev
Also, if you take one thing from this: your Signal group is not safe, even if it's highly vetted. It is NOT safe.
There is a fed in there, and even if there isn't a fed, there may be a comrade who might sell you out to avoid their own sentence.