Current Status of Catalina 10.15.3: 

• h264 hardware acceleration: weird or buggy (Symptom: Avidemux can’t scan timestamps in transport streams)
• mp4 system integration: buggy (Symptom: in certain cases mp4 encapulsated x264 videos cannot be opened within Ableton Live 10.x)
• Finder: weird or buggy (Symptoms: apps can’t be closed and remain open in Finder, no matter what, shutdown only via terminal then)
• SMB-Sharing: SMB1 support dropped (Symptoms: you can’t connect to your Fritz.box NAS anymore)
• Specific drivers: not [yet?] available (Symptoms: Novation Nocturne just doesn’t work at all anymore)

My recommendation: stay with Mojave a little longer, Catalina is immature. I am going back to a working macOS now and do a full restore of my properly working Mojave from mid feb 2020. Estimated restoration time for 1TB SSD: 90mins.

In case you really wanna go Catalina and burn your own fingers, let me recommend you to perform a full backup of your Mojave installation [overnight]. Depending on the disk size, this can take a cpl of hours. Carbon Copy Cloner is your tool of choice in this case…