The Alliance of Independent Authors is a non-profit association for self-publishing authors. You can join (for a fee) and access their advice and services here: https://www.allianceindependentauthors.org/
There are guidebooks, blogs, broadcasts, and a watchdog desk that can identify rogue services which overcharge and over-promise, under-deliver, or exploit self-published authors.
From their website:
ALLi, the Alliance of Independent Authors, is a non-profit professional association for authors who self-publish books.
Headquartered in London, the organization is global and growing, with a majority of members in North America.
ALLi was founded by Orna Ross, a trade-published author turned indie, at London Book Fair 2012.
Through outreach work that includes a self-publishing advice center, daily blog, active social media, weekly podcast and twice-yearly online virtual conference–ALLi’s influence extends beyond its core membership to reach of hundreds of thousands of indie authors, all over the world.
While freely circulating self-publishing education and advice to the author community, ALLi offers many Member-Only Benefits, including closed online forums, discounts and deals, guidebooks, pamphlets and campaign papers, seminars and events, contract and legal advice, and more.
An important aspect of ALLi’s work is overseeing the self-publishing services sector. We run an active Watchdog desk and Partner Member facility that vets approved self-publishing services.
ALLi also advocates within the publishing industry globally and at government level in the UK and runs ongoing campaigns to promote the interests of self-publishing authors, everywhere.