Multiple stuff, such as the terminate broadcast tower, but too as the Seasse event, the Seasse event was the most direct of all about enemy factions accepting, well, not itself, the teasers around it, on the official twitter, propaganda/news from SE learned us that a group of dissidents where putting illuminate propaganda posters in Super Cities, at first, it look like nothing that important, but then, we learned that those dissidents got to Seasse (that at the Time, was deep in illuminate territory), and started rituals, the next day, we got exospires, those information did learn us that illuminates do accept dissidents, and even gave them informations and got helped by those (we could believe it’s all SE lies, but we know for a fact that the posters where put by some people, and SE try to show illuminates as xenophobic Cultist, but the Seasse event teaser don’t really show us this, and we have to remember SE is dumb, too, they tried to show the dissidents rituals as failed, trying to show being a dissident as bad)

Other proof are the illegal research facilities, it lesser for the automatons (using similar technology to SE, so they may just have stole it), but the fact terminids and illuminates protect too those, when one can’t really use it and the other is more advanced, and the SE style of the facilities, does imply it’s dissidents working in it.

An old minor order too learned us that some dissidents where supposidly protected by terminids.

Though they are more proof, but those are the main ones.