The shifters are compatible with 9-speed sprockets and are suitable for brake shifting. If you want to continue using your old Ultegra derailleurs, it is important to know that the Ultegra ST-6500 series is a 3x9-speed system. The Shimano Sora shifters are also designed for 3x9-speed, which makes them compatible in principle. However, there may be slight differences in shifting performance when combining shifters and derailleurs from different groupsets (Ultegra vs. Sora), as Ultegra is of higher quality and more finely tuned.

In short: Shimano Sora shifters are generally compatible with a 3x9-speed Ultegra front derailleur, as both are 9-speed systems. For optimum shifting performance, however, it is advisable to use all components from the same groupset if possible.