This setting was renamed and moved to the main config file in fwupd 1.8.5:
5d38e0aeea
Without this patch, fwupd tries to migrate the config and crashes when it meets the immutable:
FuEngine migrating OverrideESPMountPoint=/boot to EspLocation
Failed to load daemon: failed to load engine: Failed to create file ?/etc/fwupd/daemon.conf.6HZBZ1?: Read-only file system
The setting was first introduced to the module in 08547ff642 to override the store paths set during build.5d38e0aeea
42930c79dd