It is published here in appimage, debian, rpm format.
There is a link at the bottom of the release notes ↓
I'm angry with libappindicator and it doesn't work. Maybe CentOS 7 can go
nothing provides libappindicator needed by github-desktop-2.3.1_linux1-1.x86_64
Use appimage format instead of rpm
For the appimage format, refer to here