It is very scary how they just updated the website overnight and UX has been changed.
Now it is clear that UX is not possible to earn, and retro credit is the only way. The date is "before end of 2024", but retro claim deadline is Dec 20. So let's say if there is no delay, but ability to retro claim UX does not open until Dec 21st, it seems like you will not get UX counted. This seems to be a very badly thought out promo and definitely a disaster waiting to happen.