dmesg:
wcte43x 0000:01:00.0: Firmware version e0019 is running, but we require version 13001e.
wcte43x 0000:01:00.0: firmware: requesting dahdi-fw-te435.bin
wcte43x 0000:01:00.0: Existing firmware file dahdi-fw-te435.bin is version e0019, but we require 13001e. Please install the correct firmware file.
So it is “just” a firmware issue. Probably easy to diagnose for anyone else but me.
Temporary solution found here
Solution is probably to get updated firmware provided by FreePBX updates.
That is missing.