Meagan Longoria has a couple of posts on designing Power BI reports to make them accessible to people who use screen readers. First up is a list of good tips:
Avoid auto-playing video or audio as that conflicts with the screen reader. If you must use video or audio, provide it in a way that requires the user to start it rather than stop it.
Be sure to format numbers appropriately so screen readers don’t read out a long series of insignificant digits.
Avoid the use of lots of decorative shapes and images within your report page that do not relay information to users. The screen reader reads each one. When using shapes and images to call out data points, use the alt text to explain what is being called out.
Meagan also has a follow-up blog post with more detail:
The data in the accessible Show Data table will render in the order it is shown in the visual, so you can control that in your design. One exception to this is when the data is rendered in a matrix rather than a table: the total in the accessible Show Data table is positioned at the top rather than the bottom where we see it visually. This is a purposeful design decision to help the user understand the total and then the breakdown of subtotals. Another good thing about the accessible Show Data tables is that tooltips are included, just like when we use the See Data feature.
Another nice feature (not sure if this is built in to JAWS or something the Power BI team added) is that if you have a report page that takes a while to load JAWS will say “Alert: Visual are loading” so it’s obvious to a blind/low vision user that they need to wait to get the full report page.
There is still a bit of work to be done to make Power BI truly accessible to screen readers.
Both posts are definitely worth the read.