Spell check is still available. It's down below right when you are making a post. It's next to Post, Preview and Spell Check.
The lower right "Spell Check" button has never worked for me (Linux OS and Firefox browser). It always generates a new but empty dialog box.When I get a misspelled word the red-squiggle-underline appears. I then "right-mouse-click" on that word and a dialog box pops up with one to several correction options.
I left click the mouse on the word with the red underline and it gives me the correct spelling.I am using Microsoft Edge and Windows 7.