For this challenge, we are asked to join the riftCTF discord chat at https://discord.gg/MTBdkqd. After joining the Discord, we find a channel called #flag.
Result: Going into the channel, we find a post by the admin containing the flag at the end.
Flag: riftCTF{sanity_check}
Note: The permissions to the channel have been changed after the challenge and the flag is unavailable now.