Arch Linux

Since systemd 247, some dependencies are now optional and could probably be moved to optdepends, see the official announcement:
https://lists.freedesktop.org/archives/systemd-devel/2020-November/045646.html

Relevant part:

* The runtime dependencies on libqrencode, libpcre2, libidn/libidn2,
libpwquality and libcryptsetup have been changed to be based on
dlopen(): instead of regular dynamic library dependencies declared in
the binary ELF headers, these libraries are now loaded on demand
only, if they are available. If the libraries cannot be found the
relevant operations will fail gracefully, or a suitable fallback
logic is chosen. This is supposed to be useful for general purpose
distributions, as it allows minimizing the list of dependencies the
systemd packages pull in, permitting building of more minimal OS
images, while still making use of these "weak" dependencies should
they be installed. Since many package managers automatically
synthesize package dependencies from ELF shared library dependencies,
some additional manual packaging work has to be done now to replace
those (slightly downgraded from "required" to "recommended" or
whatever is conceptually suitable for the package manager). Note that
this change does not alter build-time behaviour: as before the
build-time dependencies have to be installed during build, even if
they now are optional during runtime.


If I understand that correctly, at least libidn2, libcryptsetup and possibly pcre2 can be moved from depends to optdepends.