It may be helpful to think of things this way...the distinctions between UDL, digital accessibility and ADA accommodations is akin to the concept that while all squares are rectangles, not all rectangles are squares. It's a spectrum where the application may vary.

A square labeled 'universal design', a rectangle labeled 'digital accessibility, and a diamond labeled 'ADA'

Universal design serves and elevates all learners by encompassing the broadest category of accessible course design. When implemented intentionally, it has the potential to impact the largest audience, and integrates digital accessibility as a key component of its principle of representation.
Digital accessibility generally enhances the experience for everyone, but it does not inherently encompass universal design.
ADA accommodations may be achieved through universal design for learning or digital accessibility, but they always originate from an approved request specific to the individual.

Thinking back to a previous example, closed captioning for video content can fulfill an ADA accommodation, meet WCAG standards for digital accessibility, and exemplify universal design. In this case, all three principles are addressed in one action.

However, some accommodations, such as extended test-taking time, do not fall under digital accessibility standards but are specific to individual needs. (A testing accommodation utilizing digital accessibility standards might involve support tools like text-to-speech or magnification which ensure that students can interact with content effectively.)

Equity vs. Equality

Ultimately, the ideal goal for universal design is to eliminate the need for specific accommodations in the first place. To extend our testing scenario, the UDL approach might be to offer different types of assessment (a test, a paper, a presentation, etc.) that allow the student to demonstrate mastery of the concepts or outcomes in a manner that better suits them as individuals.

The UDL approach aims to make accommodations like those managed by Jamie's office unnecessary, allowing students to engage fully without requiring special adjustments that would otherwise create barriers.

Something to keep in mind when discussing accommodation - it is not providing an 'easy way out' for students. For a student going through the full accommodation process, it is rather like starting a race two laps behind their peers. Providing access via means of universal design and digital accessibility removes barriers that simply do not exist for other students, and makes the experience of higher education that much more equitable.