Topic on Talk:Forza Horizon 5
It still works as of Dec 1 on Windows Store version. If someone else can confirm for me that it's not working for steam I'll update the cheat table to fix it.
Essentially you go to Forza Vista with RT off. Then you enable it and the bit that changes from 0 to 1 is the same bit you change during gameplay.
So I'll find out by tomorrow (Thursday Dec 2) and make sure it's fixed.