The file is a raw hexdump. De-hexdump-ing this and checking the filetype in cyberchef shows it is an xz compressed file.
Using an online tool, https://extract.me/, you can extract a file from it.
This gives us the HTML for an SVG.
This SVG will form a QR code, but it's much easier to notice by replacing the #fffff6` colour with
#000000 using` find and replace.
Scanning this QR code gives some base64 encoded data. Decompress this, and you get another xz file. Extracting this gives an ASCII art for a QR code - in inverted colours. Swap the colours and scan for the flag.
We get two audio tracks.
One of them has a message about turntables in base64 in the spectogram, which seems kinda useless.
So to get the difference between the tracks, I inverted track one, then used audacity to mix and render the two to a new track (effectively subtracting track1 from track2) giving us the flag in a spectogram.
Using the same method as 1 and 2 we use spectrogram stuffs to get chunks of text in each audio clip using briefing hints (and guessing) we sort these by decreasing time length to get a string: janOHS{ahse0n1yz_k4f73p}
We then guess vigenere and uh after some trial and error (and using the flag format as a guide) i got a partial key of "summon", so i just guessed the key was summoningsalt
by the theme and also the briefing to get the flag.
I had no clue, so thought of a ton of things, eventually coming back to some physics lessons with waves.
We can use a spectrum analyser to see "the magnitude of an input signal vs frequency within the full frequency range of the instrument". I used spek (spek.cc) to do that, and it loads in the flag.