The Equation Image Absolute URLs change seems to have broken the 2020-10-17 MathJax Equation Improvements change. The 2020-10-17 MathJax change allowed screen-reading software to access the MathML which provided speech access to the math and also allowed using the interactive equation explorer (either the one built into the JAWS screen-reader, or the one built into MathJax).
LaTeX code as Alt-text on an image for mathematics isn't really an accessible alternative compared to what MathJax offers. Is this effect of disabling MathJax an unintended regression or is Instructure moving Canvas backwards on STEM accessibility?