Hi @mikek53457459,
Thanks for the update. Since rolling back worked for you, it does look like the problem is tied to Illustrator 29.8.1 on Windows 11. Could you try updating again and then reset the font cache using the steps(in the link) Anubhav shared earlier? It would also be very helpful if you could grab a screenshot of how the fonts appear in the previous version and then another one after updating for comparison. Please also confirm if this happens with all system fonts or just certain ones not showing up.
Looking forward to your update.
Abhishek