You ought to read the ATS forums, if you're not already a lurker. We've had all sorts of insiders and experts on over the years. Lear used to post on there, as has Bigelow. Some military guys and scientists, too. Many that stay anonymous. The archives are handy to trace back timelines and get a sense of things. https://www.abovetopsecret.com/forum/
Very risky for "insiders" to post something online. The number of people involved in retrieval of NHI technology will be small. Easy to keep track of by I guess CIA who is tasked with that job. CIA has the money, people, and means to do such things.
The number of people who are involved in reverse engineering attempts probably is much bigger. Anything online leaves a trace. CIA can try to follow who's breaking NDAs. Or they can lure people who want to release info online. By starting a UAP forum for example. Or a closed group on social media. Oldest trick in the book. That way people who talk too much come to them and can be trapped.
The threats to insiders who come out with info or evidence are real. Including being found having committed "suicide" or having had a lethal "accident". The CIA has to kill, in order to keep people in line and scared. Only barking but never biting will not work.
Their threats have to be taken seriously.
Journalist Michael Schellenberger has stated his sources were terrified before and during their meetings with him. They did everything possible not to be tracked or followed or discovered. Not just fear for their job, career and pension, but that very serious harm would be done to them by whatever organisation that is responsible for keeping things under wraps.