If you’re on HBOOT 1.15 or 1.19 on your HTC EVO 4G LTE, we mentioned last week that a downgrade tool was in the works. While an all-in-one tool has not been released yet, for those with Linux or comfortable burning a Linux live-CD, a toolkit has been made that will get you downgraded.

The steps are relatively straightforward: boot Linux, download package, unzip, change the file mode to executable, run, follow on-screen instructions.

The whole downgrade process takes about 10-15 minutes, after which you should be left with a phone with the old firmware and the ability to achieve S-OFF by feeding the Panda.

Unfortunately, you’ll still need an unlocked bootloader in order to roll back the hboot that enables you to exploit and achieve S-OFF. Unfortunately, that means the phone will be wiped unless you’re already unlocked. You can make a backup in ICS and restore via Titanium afterward, however.

The whole process to achieve S-OFF without losing any data on an unrooted phone – that’s an impressive series of hurdles you have to face, and hopefully we’ll get automated options to handle this from start to finish. But for now it’s still a major pain to accomplish.

One thing to remember, though, is it is doable. As long as it can be accomplished, it will be with how these things are done in the EVO world.

The developer of the tool does give a warning that this may set fire to your house, so do make sure to have a fire extinguisher handy, or at least read the directions from start to finish as, for the moment at least, it’s complex.