It was forked around a year or more back I believe. They are completely different projects now imo. Photon aims for the best UX and speed, while Tesseract aims to be as feature-rich as it can.
Comment on Which Lemmy instances use Photon?
Kalcifer@sh.itjust.works 1 month ago[Tesseract is] a Photon fork.
TIL that Tesseract is a Photon Fork.
Xylight@lemdro.id 1 month ago
FundMECFSResearch@lemmy.blahaj.zone 1 month ago
I think @ptz@dubvee.org might answer. If I’m not mistaking they are the main dev.