Version: Joplin for Desktop (windows 10), 2.8.8 (prod, win32)
You have a "spell check" thing, and it's enabled, for English.. but when I make a spelling mistake, it doesn't underline the thing with red or do anything to show that it's a bad spelling. I've toggled it off and on, doesn't seem to help. I just downloaded this for the first time, so no previous version was on my windows 10 machine.