I’m confused about how to participate in this event.
None of the Zwift announcements mention Strava, but they also don’t have the usual sign-up interface in the Zwift app. There’s no “event card” showing on the startup page. There are lots of Group Rides for the event, but no where to “register” for it.
ZwiftInsider has an article that mentions Strava, but Zwift itself doesn’t.
So what’s the situation?
It is a challenge on Strava. In the past Zwift would do a group ride and gift you the jersey just for showing up, regardless of how many kms you did. This year is much better as you actually have to complete the 500 kms through activities on Strava.
That’s fine, but it would help if Zwift would mention that you have to sign up on Strava, since Zwift is trying to promote participation.
Strava currently won’t accept my email address to create an account, so that’s a fun experience.
Maybe Rapha should tell you since it’s their challenge to begin with 
Good point. The Zwift page for the series never says you need to use Strava.
https://www.zwift.com/events/series/rapha-festive-500-zwift
As a non-user of Strava, I recommend making your own challenge. On Zwift people use completely bogus ways of reaching 500km like banded rides, and compared to outdoor riding, doing it on Zwift is ridiculous since speed/distance is so inflated, the challenge is like doing 400km indoors at most. A personal challenge will be more meaningful.
Or finding the biggest, fastest groups they can handle and spending all day with them. I saw that this morning and yesterday afternoon with folks doing the whole 500km in one ride. There are some other dubious ways people are doing the distance as well at extreme average speeds.
I will do this IRL where it is real distance and time - luckily we have decent weather for that to be not a problem.
The topic here is why Zwift didn’t communicate that the event requires a Strava account.
Does it, though?
The communication is not clear at all, but I thought it was the accumulation of 500km over 8 days on Zwift, including indoor and outdoor rides.
The “official” Rapha 500 Challenge is on Strava. That’s where you can earn your virtual trophy and other rewards: same name, different channel.
That doesn’t mean that you need a Strava account for the challenge on Zwift. Does Strava even write to Zwift? I don’t think it does. But it’s a commitment, so perhaps clarify it with support?
First of all, how someone does Rapha, has nothing to do with the question.
If you don’t think it’s a valid challenge, then you shouldn’t do it. And those that think, If you don’t ride outside, you aren’t really completing the challenge. Come on
Where some of us live, it’s -20 outside, with lots of snow and ice. Don’t even get me started with Wind chill. Good luck riding outside. Not happening.
I’m doing it, and it will probably take me about 17+hrs. I think that’s a fairly valid challenge. I gotta work on Monday. So it will be 3½ hrs per day, on a trainer. My Butt hurts already 
Second of all, I wasn’t the first to bring that up, so don’t just single me out please. But you must admit that some people do absolutely use bogus methods in general for everything on Zwift. Go look at some of the top distance riders, particularly one who uses teleports to tops of mountains to get free extra distance (I’ve caught that person multiple times doing it with various excuses for why it was needed). If someone surpasses that rider, then I’m sure they will find a way to start doing 3000km/week and do it week in, week out. That’s just the surface of it.
The “methods” some of them use take the shine away from those who the right thing which you are doing.
This is one great marketing ploy by Rapha…
On the ZwiftInsider Information did you check out the comments at the bottom?
From Eric
“Zwift is definitely NOT tracking the in-game kit awarding using Strava. Sorry, my comment above was unclear.
Join the Strava challenge to track Festive 500 completion via Strava. That’s one way to track your F500 progress.
Zwift will track it on their own systems as well, for the purpose of awarding the in-game kit. I assume Zwift is tracking based on local time, like Strava is. But I don’t know that for sure.”
So if you are not interested in the Strava Challenge just do it for the Zwift in game unlock.
If it’s a Zwift event, I don’t get why is there no “register” process like every other Zwift special event or challenge.
Folks, please take your argument about indoor-vs-outdoor activities to another thread. You can even make your own for free!
It is not the first one without registration - there were more in the last months.
It would have been handy to have a km counter for those who are just riding it on Zwift.