If you open the image, and scan it with qr code scanner you’ll find
RESTCON{29a9df89e2858e5a25c83b6a00352d19}
And when you paste it to the submit, it will fail.
Check again the Note, it said FLAG IS IN PLAIN TEXT, use chiper identifier to check what is the type of this ciphertext https://www.boxentriq.com/code-breaking/cipher-identifier, you’ll find out it is a MD5 Hash, and then you could search text matching the MD5 Hash using https://www.md5online.org/md5-decrypt.html , and eventually you’ll find out the text is mirr0r. Then the flag is
RESTCON{mirr0r}