Font Manager is intended to provide a way for average users to easily manage desktop fonts, without having to resort to command line tools or editing configuration files by hand.
While designed primarily with the Gnome Desktop Environment in mind, it should work well with other Gtk+ desktop environments.
Font Manager is NOT a professional-grade font management solution.
I would install the other version, since they're currently at parity, and the flathub version takes more space.
我用linux mint 20.2，进行了中文相关的设置。在软件管理器里安装这个软件后(软件管理器里的软件名是“字体管理器”，0.8.7 )后，界面是英文的，安装另一个软件“FontManager”（0.7.7-0.3）后，界面是中文的。这两个软件重要的是可以直接将windows中的fonts文件夹拖到“preferences”的“Sources”中以添加新的字体源。Ubuntu Kylin里自带了这个软件，我在那里用过这个功能。
It's better than the other version on here, but it crashed on me. Also, I've no idea what the functions of most of those settings are.