Just updated my R7800 to the latest Kong build coming from the prior version, so Sysupgrade method.
All looks good and QoS seems to work even better. Kong does not publish a clear changelog, unless you consider the Manifest file to be informative.
On bufferbloat tests with DSL Reports and Waveform, Cake QoS seems to hold up even more nicely with A+ results across the board. There is no other firmware for the R7800 that I see these results with. The graphs on DSL Reports for example are flat as a pancake, even when running a "gigabit" test on my cable line.
Find the files here: http://desipro.de/openwrt/19.07/
Thanks Kong!