I just noticed that the registry launched a new version of its website: https://roar.rugby/ so I went through the procedure of registering a domain name and it appears that...it's working.
A strange launch phase
For those interested, here is the launch phase which explains WHAT, WHEN and HOW MUCH. I found - yet - no list of accredited registrars to .RUGBY domain names but I am confident that it is coming.
I first thought that .RUGBY was a closed TLD but it appears that it is open to all (...)
There is an interesting phase called "Limited Registration Periods" which is typically what a client for a registry would want to have for a TLD like .RUGBY and I understand this choice. Unfortunately these phases have proved that they just don't work in terms of registrations: no one buys domains when it is so restricted and complicated. This phase started in January 2018 already and there are 3 in total. They end on the 28 of June 2019! As of today, there are 19 domain names registered in total.