Hi CHBMB,
thanks for your reply.
I got it working again ... with some messing around.
TL;DR: The LibreELEC 6.3.5 build seems to be missing the "smipcie" kernel module
Long Version:
I compared the loaded kernel modules of the libreElec 6.3.4 and 6.3.5 build.
All the dvb related modules were not loaded.
Then I tried to load the missing kernel modules and it seems the 6.3.5 build is missing the smipcie module.
modprobe smipcie
modprobe: FATAL: Module smipcie not found in directory /lib/modules/4.9.30-unRAID
since the TT S2 4200 is identical to to the DVBSky S952 V3 it makes sense that it doesn't work without this module.
I then tried different builds to see if the smipcie module is included in one of them so I could copy it...
The TBS (Open Source) 6.3.5 build includes the smipcie module but is missing the firmware files for the card.
Copying the smipcie.ko and "insmod smipcie" (also loading the dependencies first) didn't work. All the needed modules were loaded but for some reason the firmware didn't get loaded.
So i just copied the firmware to /boot/config, installed the TBS (Open Source) build and copy the firmware in the /boot/config/go script to /lib/firmware. Now its working again , but not the preferred way to get it working i guess
Hope this helps you to fix the LibreELEC build.