Check out items labeled Good First Issue for issues which should only require a good flutter knowlage, but shouldn't be enourmously complex or require deep knowlage of the inner workings and design of the app.'
Issues labeled blocked are mostly related to data handling, which is currently undergoing a thorough rewrite, and any work done now would have to be discarded, and will be much easier after the data update is finished.
Others, such as accesibility, could technically be worked on now by anyone, but probably require more familiarity with the app, as well as an idea of all the accessibility stuff.
Keep an eye on priority via the Roadmap project.