Hello,
I tested this out with adding French to my languages. So you could try it out?
You need to add your chosen language to the Editor and move it to the top (so its default) to then use the spell check.
see below - error has been highlighted. My preferred language is English so I need to add French via the Editor

Go to options (main menu bar) > Editor> Editor Settings > manage spellcheck languages > add another language

Added French then clicked on 3 dots on the right side and moved French to the top

Click on Done and now you should have spell check available for your chosen language
Left click on the highlighted misspelled word - I get options to change the spelling

I also tested if both English and French languages are available via spell check so added a sentence with a mispelled word in English

Both French and English spell check are available by left clicking on the mispelled word
Hope this helps.