Also, while it's good that you bring up accessibility on threads like this one, I don't think it's a good idea to go straight for the threat of legal action. The natural response to that tactic is to question whether there will really be legal reprocussions, and that's a distraction from the real issue. Instead, I tend to focus on the moral problem of blocking people from doing their job, getting their education, etc.
I never heard about any "usual disclaimers", what exactly are you referring to?
AFAIK nobody is going to be suing developers for their software and the worst that can happen is people with accessibility needs simply not using your programs. The main issue is with employees with accessibility needs being unable to perform their work due to your software and having no other alternative - this is a case where their employer (not you, unless you are said employer) can be sued.
But beyond that i never heard anything about requiring legal advice before using any sort of UI framework for general professional use (TBH that sounds absurd).
In practice the worst that can happen to you is people with accessibility needs not using your software.