Same here. 2.7K footage from drone to PC and uploaded to Youtube, and after processing it was just 1080p.
Tried to re-encode the file and followed Youtube video format guidelines recommended by Google: 2K (Exact 16:9), Progressive, 30fps, downgraded bitrate to 16Mbps... Etc... In the end, YouTube just processed a bit longer and gave a max 1080p video.
Edit:
Weird... for a few days now YouTube said it isn't doing any "processing" but now, a week after the upload, it finally gave me the 1440p (2K) option. Odd...