Flatpak is a packaging system for Linux and is one of the most popular and preferred ways of installing apps. Flathub is a repository for Flatpaks and while Flatpaks are not exclusive to Flathub, most applications available as Flatpaks can be found there. Many popular Linux distros such as Pop!_OS and Linux Mint have the Flathub repository included and enabled by default and most Linux users will add it themselves if it is not already installed on their distro. Flathub currently has an unofficial Bitwarden app maintained by community members. I believe this poses a serious security risk and Bitwarden should take over development themselves. There are currently 1000s of Linux users using the Flathub version without realizing that it is community maintained and unofficial. So the benefits of Bitwarden having an official Flatpak are:
It would give Linux users another easy and convenient way to install Bitwarden, especially since many Linux users prefer Flatpaks over other distribution methods.
It would protect the many Linux users currently using Bitwarden from Flathub without knowing the risks.
Flathub encourages developers to maintain their own applications and all Bitwarden would have to do is contact Flathub to discuss transfer of ownership.