People have had success with getting Ryzen with Windows 7, but it takes some effort.
With the Ryzen Raven Ridge APU's... ain't going to happen at all with windows 7.
With 7 coming closer and closer to EOL, it's really not worth that much trouble to get 7 onto a Ryzen cpu.
Gigabyte does provide support for Windows 7 on the download page for that mobo...
Windows USB Installation Tool
(Note) Support AMD X470/B450 series motherboards.
OS: Windows 7 64bit,Windows 7 32bit