If you want to package the software for distribution, a few adjustments/patches are recommended:
If you install default configuration files, you might want to
adjust [NFTABLES] exe = ... to the absolute path of your
nft binary. See the
configuration documentation for more details.
You probably want to install the systemd units under
/lib/systemd/system/ or similar, instead of
/etc.
The build environment variable LETMEIN_CONF_PREFIX
sets the prefix for the configuration files. In a plain
cargo build this will default to / meaning
that /etc/letmein{,d}.conf will be the place for the
configuration files. If you use the build.sh script, the
prefix will be set to /opt/letmein instead. Meaning that
the configuration files will be placed into
/opt/letmein/etc/.
Adjust the install prefix from /opt to something
else that makes more sense for your distribution.
It is highly recommended to keep the
overflow-checks = true and panic = "abort"
cargo release profile settings, as they are important for security
hardening of letmein. If you want to adjust them, make sure to
understand the security implications of doing so. The other settings in
the release profile can be adjusted as needed. But it is recommended to
also keep the other settings as they are.