[darekkay]

You can always get a first impression by checking a website with Chrome Lightroom. For Mantine, Lightroom returns a few ARIA and a lot of contrast ratio issues. NextUI is built upon React Aria, which indeed puts accessibility first. Nonetheless, NextUI includes some contrast ratio issues as well. I think that claims like "fully accessible" or "exceptional accessibility" give a false sense of security to people using those UI frameworks. Accessibility is not something a UI framework can guarantee for your app or website.

EDIT: I've added Mantine to my post. I've left out NextUI, being more of a "skin" over React Aria.