Here are a few links to information about Gutenberg and a11y:
Report on the Accessibility Status of Gutenberg
In the short term, we hope to resolve all accessibility issues that are true barriers to the use of Gutenberg. In the long term, we hope to improve the integration of accessibility into all future WordPress design processes.
and https://design.oit.ncsu.edu/2018/10/24/gutenberg-accessibility/ NCSU recommends not switching yet…
Hope this is helpful information to share @ned and @jhung and @SteelWagstaff and @zoe