Thomas left a message and it seems that the Heiwa/Peace firmware works on his LS-XL, although since the device is too slow for Plex, he could only confirm the integrity of the firmware.
It’s a good start but I’m still waiting for more feedback to confirm that everything is fine with this firmware. So far no issues were reported which is also a good sign.
If you have a spare hard drive, please try installing this firmware by removing your hard drives (to make sure your data is safe) and inserting the spare hard drive, then flashing the firmware. A lot of people would like to use Plex for Christmas and the latest Plex is compatible with the new Apple TV too.
If you decide to upgrade the firmware with a spare hard drive, you have to make sure it doesn’t contain partitions and that you can change the IP address of your PC. You can find the details to install a Linkstation with a blank hard drive here.