Answering myself, but mainly to help someone,
I managed to activate lane assist via long coding (have not tried in practise whether it will really work). None of the Apps "Lane Assist" or "Lane Assist V2" worked. For long coding I used the instructions from page 60 (because I have camera MQB_B_MFK) from OQB Kodierungen
www.motor-talk.de/forum/aktion/Attachment.html?attachmentId=779654Here is a translation (using Google translate, so it might have mistakes):
Lane keeping assistant (Lane Assist) - activation (variant 2)
Multifunctional camera (control unit A5 - "MQB_B_MFK") must be installed, e.g. E.g. installed when ordering with DLA and/or VZE! Once the coding has been completed, you should wait for the bus to rest. Coding in STG 10 is only necessary if the corresponding bit is labeled this way or errors remain in the STG.
STG A5 > Coding > Byte 16 > Activate bit 7 ("Lane keeping assistant (HCA) active/installed [PR-7Y9]")
STG A5 > Access permission: 20103 > Customization >
...
> Channel "Personalization time of intervention at terminal 15 on" > Set value to "Last setting". > Channel “Personalization BAP” > Set value to “not active”.
> Channel "Lane keeping assistant switch-on status" > Set value to "on (setting via menu)".
STG 5F > Customization > ...
> Channel "Car_Function_List_BAP_Gen2-LDW_HCA_0x19" > Set value to "activated".
> Channel "Car_Function_List_BAP_Gen2-LDW_HCA_0x19_msg_bus" > Set value to "Data bus Extended".
> Channel "Car_Function_Adaptations_Gen2-menu_display_Lane_Departure_Warning" > Set value to "activated".
> Channel "Car_Function_Adaptations_Gen2-menu_display_Lane_Departure_Warning_over_threshold_high" > Set value to "activated".
STG 17 > Coding >
...
> Byte 04 > Activate bit 6 (“Lane keeping assistant / Lane Assist installed”)
> Byte 11 > Activate bit 1 (“Lane Keeping Assistant / Lane Assist Information (BAP) installed/active”)
STG 44 > Access authorization: 19249 > Coding > Byte 03 > Activate bit 0 ("Lane keeping assistant installed")
STG 10 > Access authorization: 71679 > Coding > Byte 03 > Activate bit 5 ("Lane keeping assistant with steering support installed")
NOTE: My car does not have STG 10, I do not know what it is ...
Disclaimer: use at your own risk!Edit: tried next day and Lane Assist is working