In the final episode they will reveal their solution and it airs on tuesday I think. Their trailer etc however, hinted with enough material in order to start have a look.
Trailer: https://www.history.com/shows/the-hunt- ... is-cracked
From screengrabs I reconstructed the following

Rough transcription would be:
HERE IT IS I KILL BOTH
NIGHT AND DAY . I LIVE
BY THE GUN BAREL AIM
SO OUT TWT(?) SHING FOR G
AME TUR(?)O YER PIG IS M
IN I LOCK S ? NOW
DANGEROUS _____
HANDGE__YO_GAME
....
...
and towards the bottom they say they found a "name":
RICH
ER DMNI KSON
(name "richerd m nikson" as in "Richard Milhous Nixon", the president?)
So, they don't mention any methods used but by looking at the picture it should become clear.
This is just a pipe dream.
* They let some cipher letters remain unchanged in the cipher code. Other symbols are rotated or mirrored (message starts with "HERE" ... cipher starts with "HER". This is the only pattern in their solution)
* They squeeze in extra letters when needed, and ignore cipher text when it doesn't fit their goal (on line 8 they did this twice in order to create some plausible text)
* Symbols change meaning right and left, only to make the imagined words appear in the text (eg the + on row 5 & 6 is F and G. Why?)
* They are seriously just making shit up
