Here's the list of notable changes in TeX Live 2026 [0]. LaTeX is released independently from TeX Live, so looking through its changelog [1] is also helpful if you haven't updated recently.

[0]: https://tug.org/texlive/doc/texlive-en/texlive-en.html#x1-94...

[1]: https://www.latex-project.org/news/latex2e-news/ltnews.pdf#i...