For this challenge, we are told that the flag is hidden on a post on LinkedIn. Lucky for us, LinkedIn has a search function, allowing us to directly search "riftCTF{" and find all posts containing the flag. 
https://www.linkedin.com/search/results/content/?keywords=riftctf&origin=SWITCH_SEARCH_VERTICAL
Result: We find a post by a page called Ciphercell containing the flag.
Link: https://www.linkedin.com/posts/ciphercell_ciphercell-cybersecurity-activity-6633997672254660608-tVEH 
Flag: riftCTF{W3lc0me_t0_c1ph3rcell}
Note: Post has been edited after the challenge and the flag is unavailable now.