You can install and use Bazaar from the Nobara Welcome App --> Recommended Additions. Flatpost may also be installed by default.
The KDE version of Nobara additionally comes with plasma-discover which can alternatively be used to manage flatpaks. It is not able to manage system packages.
The GNOME version of Nobara additionally comes with gnome-software which can alternatively be used to manage flatpaks. It is not able to manage system packages.