Request Tracker, an open-source issue tracker we use at work, has had almost completely inaccessible dropdowns ever since 5.0. In the last couple days, I've been poking around, trying to work out why. They use Bootstrap 4.6, which is way behind, and even Bootstrap 5.x seems to have accessibility problems. They take an unordered list, a text input, and a hidden input, and try to simulate a select element. You know what's fully accessible? A SELECT ELEMENT! Just use what's already there, people!