This ownership change was spotted on the r/Ryujinx Reddit forum by user XeClutch, who shared a WHOIS database screenshot showing Nintendo of America as the emulator's main 'Registrant Contact'.
WHOIS data indicates the domain information was last updated on November 7th, though Nintendo may have acquired the Ryujinx site earlier.
The emulator site is no longer working. After announcing its shutdown, the Ryujinx site stopped offering emulator downloads, but kept the domain active. While the site remains blank, Nintendo's formal ownership likely aims to prevent future emulator downloads from the domain.
In late October, a new Ryujinx update appeared on its GitHub page, hinting at ongoing emulator development. Though Nintendo now owns its website, this doesn't necessarily mean Ryujinx is completely finished.