Hi there! I see you're having trouble finding the Synology Photos app on your Amazon Fire TV Cube. Just to make sure we're on the same page, could you tell me if you are trying to install the official Synology Photos app directly from the Amazon Appstore on your Fire TV Cube? Also, is your Synology NAS running DSM 7 or newer?

From what I know, the older DS Photo app that used to work on Fire TV devices is no longer compatible with Synology Photos, especially since DSM 7 merged DS Photo and Moments into Synology Photos. Currently, there isn't an official Synology Photos app available for Amazon Fire TV devices, including the Fire TV Cube.

However, you do have some alternative solutions:

1. Casting from Mobile Devices: You can use the Synology Photos mobile app on your smartphone and cast photos and videos to your Fire TV Cube using compatible apps or mirroring functions.

2. Using Third-Party Apps: Consider installing media player apps like Kodi on your Fire TV Cube, which can access your Synology NAS media files via network protocols like DLNA or SMB shares.

3. Access via Web Browser: Since you’re on Windows and using WebKit browser, you might try accessing Synology Photos through your NAS’s web interface on other devices or on a browser-enabled TV.

If you want, I can guide you step-by-step to set up casting or Kodi for accessing your photos remotely. Does either option sound like something you'd like to try? Also, if your setup or goals are different, let me know so I can tailor the advice better.

Would you like to proceed with any of these options?