This one is simple! Just look where you might look at the cryptographic history of the sunshinectf.org domain! There’s a Yeti in one and a Nimbus in another!
Flag Format: sun*endflag example: sun-this-is-the-flag-endflag
With a name like transparency its gotta be certificates. A certificate search for the root domain sunshinectf.org on https://crt.sh reveals the flag.