2160p (Native 4K), derived from a true 4K digital intermediate. Reviews from Cineluxe note that because it was shot on 65mm and IMAX film, the picture has a natural, cinematic look with minimal film grain.
For a detailed breakdown of how the 4K transfer handles the IMAX sequences and the controversial audio mix, check out this technical review: Tenet [4K UHDrip][2160p][HDR10][AC3 5.1 Castell...
AC3 5.1 in Spanish (Castellano). Note that Christopher Nolan intentionally avoids Dolby Atmos for his films, preferring traditional channel-based audio. 2160p (Native 4K), derived from a true 4K