@JoshsJunkDrawer welcome to the forum.
You are not alone, this is also happening to me. I did make a reference to it in another post a few weeks back but I have not had the time to raise a GitHub issue. It seems that the markdown editor (not legacy) spellchecker stopped working with 3.6.14. Revert to 3.6.13 and the spellchecker works as normal. I do not know if it is also broken on the Windows & Mac clients.
EDIT:
This is possibly a Linux issue as the markdown editor spellchecker appears to work normally for Joplin Desktop v3.6.14 on Windows