The link on the first page: http://www.flashtool.net
9.28 didn't work for me, but 9.25 worked well, here is a list of changes and a link to 9.25
Updated JDK to 13.0.1
Updated libusb to 1.0.23 for Linux and MacOS
Updated usblogparser to be more accurate
Compatibility with Xperia 5
Updated internal libraries
Support for XZ3 and X1
Updated JDK to JDK 13 and switched to OpenJDK on all platforms
Updated to latest Eclipse platform
FTF created with very old releases of Flashtool are not compatible with the new version.
I've heard flashtool not beeing compatible with old devices
Thats not true. It's just the bundle that is not shown.
As a workaround, extract the bundle content to a folder.
If the bundle contains a boot folder, rename sinb and tab files to sin and ta.
Recreate the bundle with the new Flashtool
Update for XZ2 and XA2 series. For XA2 or XZ2 flashing
You will have to recreate the FTF with the release 0.9.25.0 of Flashtool if you already had a FTF
Updated all libraries to latest version
Updated Java to 10.0.1