Web content is no longer accessible to screen readers in Tor Browser for Windows

Summary

Web content is no longer accessible to screen readers on Windows. One can tab through elements in the focus order, but cannot read the document or non-focusable elements fully as in previous versions or other web browsers like Firefox.

Steps to reproduce:

1. Open Tor Browser with a screen reader, such as NVDA, running.
2. Try to browse any website (not internal firefox tabs such as about:config) in "Browse Mode" using the arrow or document navigation commands.
3. ... The document will not be read, only focusable elements when tabbing through them, no matter if "focus" or "browse" mode is enabled.

What is the current bug behavior?

Web content is not accessible to screen readers.

What is the expected behavior?

Web content should be accessible to screen readers as in previous releases, not just focusable elements.

Environment

OS: Windows 10

Installation method: Update from previous version, also tried installing the latest alpha with no fix.

Tor Browser Version: 12.0.4

Relevant logs and/or screenshots