After testing several other kernels, I think I have found the root cause: Geode LX does not support PAE. How could I have missed that, sorry for the noise. I don't know how to close this bug properly myself.
- Bug#915862: linux-image-4.18.0-3-686-pae: Doesn... Gert
- Bug#915862: linux-image-4.18.0-3-686-pae: ... Gert
- Bug#915862: linux-image-4.18.0-3-686-pae: ... Gert
- Bug#915862: marked as done (linux-image-4.... Debian Bug Tracking System