Do retail investors really have a choice at this point? When I opened my Schwab account there were fees for each trade, but now it's free like most (all?) others. The only broker I know of that doesn't sell order flow is Interactive Brokers, and they restricted $GSE anyway (to "protect themselves").
A judge can not dismiss a civil suit due to lack of evidence until after the discovery phase since until that phase no evidence is even produced or evaluated. Prior to discovery all that a judge can evaluate are the statement of claims with damages and procedural matters such as standing, jurisdiction, proper service, etc...
There are claims of wrongdoing alleged in the lawsuit, notably that Robinhood has two classes of customers, its users who buy and sell securities using its app, and financial institutions who pay Robinhood for information about those users. The allegation in the lawsuit is that recent trading on GME by Robinhood app users resulted in a conflict on interest towards Robinhood's institutional clients, and that Robinhood halted trading in GME and other stocks to benefit its institutional customers at the expense of its app users. Given that Robinhood has a fiduciary duty to its app users and no such duty to its institutional clients, that conflict of interest was a breach of its duty and Robinhood must be liable for any losses arising as a consequence of that breach.
That is a claim of wrongdoing. In almost any non-trivial lawsuit, evidence can only be gathered after claims of wrongdoing have been made, at which point both parties are compelled to disclose vast amounts of information that could be pertinent to determine what damage has been caused.
Citadel Securities LLC (market maker) has a relationship with Robinhood, Citadel LLC (hedge fund) the one with the short doesn't. Read into this what you want.
https://www.pcmag.com/news/robinhood-faces-class-action-laws...
Be aware of the risks upfront when doing business with a company when you're not the real customer.