The big "problem" for me with Catalina is its loss of support for 32-bit addressing. And with Mojave I'm happy to be able to use a number of 32-bit applications that have no 64-bit "upgrade", including the TexEdit text processor that rulnacco mentioned just above. I'll continue to review my software in view of available 64-bit versions. Should I fear being an old fogy stuck in the past? 
Timmyjoe
Veteran
Running into one problem running Lightroom 5 on Catalina, can't import RAW files directly from my Z6. Need to run them thru DNG converter first. There is no way to upgrade Lightroom 5's RAW converter to handle the Z6 RAW files.
Best,
-Tim
Best,
-Tim