Plinth goes into restart loop after upgrading to 19.10

Architecture: amd64
Debian: buster/testing

I upgraded the freedombox package from 19.6 experimental to 19.10 experimental.

• Downloaded the package from snapshot.debian.org
• Installed using gdebi
• Was shown a config file prompt about two Apache config files for Searx. I accepted the maintainer's configuration (the one from 19.10 package).

The Plinth service shows up as started in systemd, but keeps restarting itself every few seconds in an infinite loop (as observed from journald logs).