TerraMaster Forum

Here's another approach that may help.
Before installing Emby from the App Center, make sure to click the Refresh button (see screenshot below).

Thankyou again for taking the time to investigate. I'll give Terramaster credit they really do take on board and try to investigate these issues! For me (after a lot of testing), I finally managed to get Emby working correctly on my F6-424 with TOS 7.

In the end, the solution was:

Completely uninstall Emby.
Delete all old Emby data (/Volume1/Emby, any old -ffdetect data, cache files, etc.) so there was no previous configuration left.
Install the latest TerraMaster-compatible Emby package (v4.9.5.0) downloaded directly from the Emby website rather than the older App Center version.
Initially, Emby still had problems after reboot because the launcher wasn't passing a valid ProgramData directory, causing Emby to create its database in the wrong location.
I modified the launcher script to explicitly set:
APP_DATA_DIR="/Volume2/Emby"

instead of dynamically calling:

APP_DATA_DIR=$(ter_share_add -name "Emby")

After that, Emby started correctly with:

-programdata /Volume2/Emby

and now stores all of its:

database
metadata
artwork
cache
plugins
logs

under:

/Volume2/Emby

which is exactly what I wanted, as my applications are installed on an NVMe storage pool.

I've now rebooted the NAS several times and Emby continues to start normally every time.

Important note for TM Firmware Team:

Although this workaround has completely solved the problem for me, I believe there is still an underlying issue with the package or launcher. It would be useful if the launcher handled a failure of ter_share_add more gracefully rather than starting Emby without a valid ProgramData path.