Is Catalina fully operational ?
I was wondering if the OS Catalina is supported by adobe and presonus ONE software.
I just got a 2012 IMac A1419 27’’ on eBay and I want to know if I can use it.
You'll have to check with Adobe and PreSonus to learn if their products are compatible with Catalina.
IMHO, that iMac is not a wise purchase as it cannot be upgraded beyond Catalina, an OS that is on its last legs at Apple. You'd be doing yourself a favor to return or resell it and find a Mac that is no more than 5-6 years old.
Catalina IS fully functional, but it's up to Adobe and PreSonus to make their product work properly.