MathML has been integrated into the Chromium engine, which powers browsers like Chrome, Edge, and Brave. It allows to render mathematical formulas in the browser without the use of additional JavaScr*pt libraries. Browsers supporting MathML should display the formula below as a summation on the left-hand side and as a product of an “m” and a second order derivative on the right-hand side.
Now, all major browsers will support MathML. To ensure no one is left behind, I plan to wait a couple of release cycles before transitioning away from using KaTeX on this site in favor of MathML. I will have to check, but it should probably be possible to convert LaTeX to MathML with pandoc (MathML is not nice to write in).