Shameless bit of self advertising but here's my brilliant theory.
Nomads threw the whole 'lets be subtle' thing out the window in vanilla. Rheinland doing what it did has no other rational explanation for the various incursions it supposedly made into Liberty, Kusari and Bretonia. And lets be honest, given the 800 year history of Sirius, I would imagine someone somewhere would have asked the question: Is this normal behavior? The logical answer being 'no, of course not'. Even Gallia, with all it's might, isn't mad enough to attack all 4 houses at once. So by that logic, someone must have come up with a reasonable explanation as to why Rheinland did what it did in vanilla.
However, the question as to 'is it public' is more or less straight forward. The various Military's and intelligence factions know about Nomads, the Core and the Order, know about nomads. The Outcasts, the Corsairs, the Zoners and presumably the GMG to a limited extent, would have knowledge of them. What is that if not public information? Sure, nomads have their fair share of secrets, where they live, how they came to be ect, but an all out suppressed secret? Seems highly unlikely given the current state of affairs. Plus you can tie it into the fact that people now (21st century) believe aliens are out there, and why would that belief change a couple hundred years down the line? I mean, you've got people now saying 'aliens did it' so presumably you'd have similar people in Sirius saying it as well, but with a hell of a lot more validity than old Billy-Bob telling us a yarn about how his cousin Hank went to the pub for an hour, woke up in some ditch and because he didn't remember how he got there, aliens must have been involved.
Wilde on the other hand, completely different. Spotting them, identifying them as infected ect...not something you can figure out in a passing ''hello''. But Nomads being public knowledge? I'd say so, more or less. Remember, 99% of the people on Texas probably wouldn't care even if it were true.
It would have been the biggest wtf of recent history. But two factors govern its secrecy. those who were directly affected by the incidents and seeing alien ships and every single one of those people affected staying silent for decades. The order was blammed for setting off that war with Rhineland as is and is a vary convenient cover. Stress narrows your discernment and liberty ships being blown up in manhatten orbit and terrorist ships causing havoc is quite enough stress.
I would have no doubt every event involving nomads would have been compartmentalized highly in the intelligence circles. But the principals of those affected come down to need to know.
There are some cultural differences in sp that seem to be apparent and glaring. But realistically people will generally wish to continue with their lives.
Panic is a big issue. Body snatching aliens nearly taking over everything would just set off massive upheaval. Government succeeds purely on faith. which was rocky before 800 a.s.
So upon the rarity of being a free agent operating in space on your own the vast multitudes within the colonies who only work in space. and even lesser numbers who travel far enough to see a nomad. Those that know? would be in vary close company in house space.
Though the opposite might be true of Omicron civilizations. They might have been more oblivious of house war and nomads since the news and happenings in the edges would be somewhat mostly absorbed in their own world and struggles.
Overall? Some people cant let things go. Recoding of alien ships would be stopped or curtailed and dis information would be flooded into civilian media. true gun-cam footage of a fight with a nomad? replace it with a vary well done fake that looks just like it except dont hide its fake. etc. lame duck arguments about alien life in the universe etc. controversy and spinning heads about nomads. After all knowing about nomads isnt so much of an issue if nothing consequential comes from its truths. Memes lol. make it an old subject. and people will pass when it comes up.
Just some ideas. in sp the threat was supposedly delt with. and life went on. but in disco? well I dont think it needs to be that complicated myself.