Where can I find reliable sources about secret societies?

Bavarian state archives hold the seized Illuminati documents from the 1780s, much of it published and translated. Masonic Grand Lodges maintain libraries, several open to the public, holding minute books and membership records going back centuries.

Australian state libraries hold fraternal collections, and Trove digitises Australian newspapers back to the nineteenth century, including lodge notices and local reporting.

University presses and peer-reviewed journals in history and sociology cover fraternal organisations and conspiracy belief. Peer review is imperfect but it filters the worst claims, and citations let you trace an argument to its evidence.

Many Australian university libraries allow public access to reading rooms.

Grand Lodges, service clubs and orders publish constitutions, principles and rules. These are self-descriptions rather than neutral accounts, but they tell you accurately what an organisation asks of members — which is exactly what you need before applying to one.

The Illuminati's principles, rules and application process are published for the same reason.

Anonymous ebooks, content farms, videos with no sourcing, and sites selling membership or access. Also discount anything that quotes only other secondary sources in an unbroken loop.

The clearest warning sign is a source that has an affiliate link where a citation should be.

Confirm important claims in at least two independent places, ideally with different interests. Independence matters more than quantity — five sites copying one post are one source.

Doing this consistently is slower than believing things, and it is the only way to end up actually informed.