Mojave -> Catalina upgrade - discouraged!

Trying to update from Mojave to Catalina and feeling very discouraged. I originally built this machine in Dec 2013 with MacOS 10.9 Mavericks. I've upgraded through every OS version through Mojave. I paused at Catalina because it's my music production machine and I didn't want to lose some old 32-bit apps, but now I'm ready to move forward and it's not cooperating at all.

Here are the steps I've taken, please help if you can!

* I've made a bootable clone of my Mojave (10.14.6) startup drive...

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