'net-im/viber-20.3.0.1' with 'pulseuadio' use-flag pulls 'media-sound/pulseaudio-daemon' which conflicts with currently installed 'media-video/pipewire' which provides pulseaudio emulation.
[blocks B ] media-video/pipewire[sound-server(+)] ("media-video/pipewire[sound-server(+)]" is soft blocking media-sound/pulseaudio-daemon-16.1-r7)
[blocks B ] media-sound/pulseaudio-daemon ("media-sound/pulseaudio-daemon" is soft blocking media-video/pipewire-0.3.71-r2)
* Error: The above package list contains packages which cannot be
* installed at the same time on the same system.
(media-sound/pulseaudio-daemon-16.1-r7:0/0::gentoo, ebuild scheduled for merge) pulled in by
media-sound/pulseaudio-daemon required by (net-im/viber-20.3.0.1:0/0::nest, ebuild scheduled for merge) USE="pulseaudio -apulse" ABI_X86="(64)"
(media-video/pipewire-0.3.71-r2:0/0.4::gentoo, installed) pulled in by
>=media-video/pipewire-0.3:= required by (kde-plasma/plasma-workspace-5.27.5:5/5::gentoo, installed) USE="calendar fontconfig (policykit) screencast wallpaper-metadata -appstream -debug -geolocation -gps -handbook -semantic-desktop -telemetry -test" ABI_X86="(64)"
...
'net-im/viber-20.3.0.1' with 'pulseuadio' use-flag pulls 'media-sound/pulseaudio-daemon' which conflicts with currently installed 'media-video/pipewire' which provides pulseaudio emulation.