ChirpStack OS - Static IP, layered filesystem

Hi,
How can I set a static IP in ChirpStack OS? The most obvious way, modifying
/etc/network/interfaces
does not work. The modified file is saved correctly in the layeredFS, but ignored at startup. I do know workarounds for this, but I am really interested in the origin of this problem.
One option would be that the interface-configuration is set up before the layeredFS. Hardly denkmöglich, since the layeredFS should be available at a very low runlevel …