These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.95 s (backtrack: 0/20).


!!! The ebuild selected to satisfy "<dev-libs/libratbag-0.18" has unmet requirements.
- dev-libs/libratbag-0.17-r2::gentoo USE="-doc -elogind (-systemd) -test" PYTHON_SINGLE_TARGET="python3_12"

  The following REQUIRED_USE flag constraints are unsatisfied:
    exactly-one-of ( elogind systemd )

  The above constraints are a subset of the following complete expression:
    exactly-one-of ( python_single_target_python3_12 ) exactly-one-of ( elogind systemd )

(dependency required by "app-misc/piper-0.7-r1::gentoo" [ebuild])
(dependency required by "=app-misc/piper-0.7-r1" [argument])