I’d been holding off putting Catalina on the iMac, cos I still wanted to access some old 32-bit apps, mostly games. Then I read an article on Apple News thet indicated for a Mac to participate with file & folder sharing in its iCloud drive, it had to be running 10.15.4. This was the impetus for upgrading. I had been cloning the iMac to an external SSD, that being a 512 GB item extracted from the dead & drowned MacBook Air. The SSD was put into an OWC Envoy case for use as an ext drive.
This drive has become my way to access those 32-bit thingies & a new 500 GB Seagate SSD was purchased this morning for a mere $99. SuperDuper! app is making its first clone right now.