When one tries to install https://store.kde.org/p/1167639/ via "get new theme" in System settings it will silently fail. The reason is that arc-kde-plasma.tar.xz have two themes inside: Arc-Color and Arc-Dark. However icons packs and window decorations packed in the same way (more than one folder in one archive) are installing fine icons https://store.kde.org/p/1166289/ window decorations https://store.kde.org/p/1167637/
This seems to be working now.