I'm running macOS 10.14.5
I have been on Kindle 1.23.1 and have had everything running smoothly with Calibre 4.1 (and today's update of 4.2 worked too). I have Alf's 6.6.3 Calibre plugin working as well and have had no issues downloading KF8/AZW3 files with this set up.
I decided to see if I could get things working with Kindle 1.26.1 before attempting to update to Catalina and so far everything is working as it should. I ran chmod -x and am still downloading KF8/AZW3 files with the right-click download option.
However, I now get an error code every time I close/quit K4Mac. "Kindle quit unexpectedly." It has a long list under the Problem Details which is total Greek to me.
I decided to re-download 1.26.1 fresh from amazon's website and reinstalled 1.26.1 and am still get the same error code, though aside from this issue upon quitting the Kindle app things seem to be working.
Anyone else run into this? Did you figure out the issue?
I am hesitant to move forward with installing Catalina at this point.