Philips tv with titan os

Hi everyone,
Has anyone ever been able to get this type of TV to work in HA?
I use the standard Philips TV integration, which installed fine without errors or problems
But the TV simply isn't responding to any of the commands
The TV runs Titan OS with API version 6.1
The TV responds to a call on "http://10.99.99.52:1926/system" and shows, amongst others, the version of the API
I've been working on this for the last week and am getting nowhere ...
Even something which should be simple like selecting the input or source doesn't work
If I go to "developer tools/States" and filter on the TV entities, there isn't one that shows the available sources

Can anyone help me? (before I lose my mind :upside_down_face: )

If I send the following script to the tv (when it is turned on)
action: media_player.select_source
target:
entity_id: media_player.salon_65mled910_12
data:
source: HDMI 1
It gives no error or anything, but the TV doesn't respond to it either
Same thing for source: HDMI 1 or source: "HDMI 1"
I have to add the
data:
source: HDMI 1
In YAML mode, because in UI mode the drop down list of sources is empty