Why not to just start discussion. There are already 3 ppl auound interested.

There is no visible sites on hacking Panasonic FW. I suspect that's because there is simply no any Panasonic hacking done in the world at all.
Pana-bastards use free GNU/GPL open-source Linux since 2004 and publish just a small useless pieces they call 'open-source'.
Open-source license means I could be able to compile a whole product and use it, then mod it if I want to mod and use it again. All the modded sources should be published as GNU/GPL open sources.
Furthermore, license reuires to publish all the sources when an open sourced GNU/GPL code is the main part of the software.
Sure the whole linux is the main part of the TV FW which onsists of the Linux with a small mods and additions.
If 'all the sources' are open, why do Panasonic devs strongly encrypt their FW updates, so called SDDL.SEC?
These SD updates are freely available for DL only to the US/CA customers. European/Asian customers forced to pay hundreds of bucks just to perform this simpliest operation like a copying one file to the SD card and inserting that card to the TV set. That policy is impudently forced even though some sets have a FW/HW flaws preventing normal operation after a few years of use (CCFL degradation). It's a simply a fraud!
I can't find any publications on the some kind successfull experience in the Panasonic FW update unpacking for 10+years. So I realize, we should at 1st dump some FW from the working TV set and explore/reverse it just to take into the encrypting techs.