Original report: https://github.com/mattermost/mattermost-server/issues/14621
Firefox 76.0.1 on community-release using JAWS Professional Edition 2020.2004.66 ILM
If using TAB to navigate to the actual message in the post, JAWS does not read it out.
Only dates are read, but not the messages or who sent them. There are no errors or screenshots that can be produced in this situation.