Slowly but surely Catalina is starting to struggle. i have the iMac Late 2013, 16gb, 1TB, 21”. Search for Music, Movies in library is still broken, scroll bars for column view there is broken. Purchasing music does multiple downloads of the songs and stays stuck downloading, despite showing all tracks downloaded. It keeps doubling the downloads of songs-albums. iMessage loses thumbnail images on occasion or just doesn’t sync with iCloud message with other devices running latest OS. Mail will take over a min or so to open preferences. Safari bookmarks no longer synch with other devices. Hardware is good, software starting to break. Will have to retire this soon. Good thing HomeSharing still works with the new stuff.