While many small companies do not pay much attention to onboarding, I'm not sure that this is the actual stumbling block.
I think the bigger problem LambaSchool graduates who've talked to me say is that LambdaSchool's poor reputation and haphazard leadership have left the value of their schooling in question, and that puts them at a material disadvantage compared to people with a traditional college degree. This is a variant of the problem that Udacity and co face: companies recruiting have reservations about that type of education and view it as a risky hire.
AFAIK (it predates my time with Udacity substantially) Udacity discontinued their active placement programs, and generally when they do that (again, I have no special knowledge) it happens because it was neither working nor cost effective.
I think LambdaSchool would be better served using its resources to improve the reputation of its graduates by actually highlighting their work and functioning like a more traditional university; sponsoring open source work and research and showing their graduates and produce such work. Universities get famous and reputable off the back of work like this.
They might also consider not being such shady actors, with a long history of tax disputes and illegal operation. It doesn't matter if state and federal rules are unjust; what matters here is that companies (especially smaller ones) need to maintain the appearance of managing risk. An association with LambdaSchool damages that.
Full disclosure: I don't like the leadership of LS at all. But I have a lot of compassion and respect for the individuals that have taken their destiny into their own hands and learned the trade through any means necessary. I think folks that emerge from these processes are often better members of the workforce than traditionally educated people; because of the tight selection filter (only very talented and motivated people can pass through these processes and succeed, therefore you're selecting from an inherently more dedicated and energetic candidate pool).