I used RC6 and have issues.
It successfully jb the device but the ATV no longer works. (it said it completed the JB)
The only way to get the blue light to blink is via the micro-USB, the device is a brick and sends no signal to the tv.
I am did a restore to the firmware from the jailbreak matrix site. I don’t even know if that is adjusted firmware or Original and get a successful restore message but still can not get it to work. It still has no blue light (except when plugged into computer) and the TV says “no signal” from the HDMI port.
I am now just trying to get the official apple firmware back.