An updated version of Notepad currently rolling out to Windows Insiders in the Canary and Dev channels is adding two more modern features to the old app: spellcheck and autocorrect. Per usual, spellcheck in Notepad highlights misspellings with red squiggly underlines, and right-clicking the word or pressing Shift + F10 will pop up a short menu of suggested fixes.
https://arstechnica.com/gadgets/2024/03/windows-notepads-midlife-renaissance-continues-with-spellcheck-and-autocorrect/