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

Calculating dependencies ... done!
Dependency resolution took 0.92 s (backtrack: 0/20).


The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by sys-process/gnome-usage-48.0::gentoo
# required by =sys-process/gnome-usage-48.0 (argument)
>=net-misc/networkmanager-1.58.1-r3 vala

!!! The ebuild selected to satisfy ">=net-misc/networkmanager-1.44.0[vala]" has unmet requirements.
- net-misc/networkmanager-1.58.1-r3::gentoo USE="concheck modemmanager nss policykit ppp tools wext wifi -audit -bluetooth -clat -connection-sharing -debug -dhcpcd -elogind -gnutls -gtk-doc -introspection -iptables -iwd -libedit -nbft -nftables -ofono -ovs -psl -resolvconf (-selinux) -syslog (-systemd) -teamd -test -vala"

  The following REQUIRED_USE flag constraints are unsatisfied:
    vala? ( introspection )

  The above constraints are a subset of the following complete expression:
    bluetooth? ( modemmanager ) connection-sharing? ( any-of ( iptables nftables ) ) gtk-doc? ( introspection ) iwd? ( wifi ) test? ( tools ) vala? ( introspection ) wext? ( wifi ) exactly-one-of ( gnutls nss ) at-most-one-of ( elogind systemd ) at-most-one-of ( syslog systemd )

(dependency required by "sys-process/gnome-usage-48.0::gentoo" [ebuild])
(dependency required by "=sys-process/gnome-usage-48.0" [argument])