I usually upgrade a few months after the initial release of an update since I use Delphi in a production environment. The current release came at a lull in my production cycle and since the 10.3.3 to 10.4.1 upgrade went smoothly, I decided to give 10.4.2 a spin. A minor (dot dot upgrade) should be pretty minor and the upgrades from 10.3.1 to 10.3.2 and 10.3.3 were all pretty seamless. First impression is that this is not a simple upgrade. After the upgrade the IDE would not load, throwing numerous errors about missing files. None of the 3rd party components loaded. Time to start over. I'm uninstalling and re-installing to see if it goes better. How was your upgrade experience?
Knowing which method you installed before (off-line ISO install versus Web install) I think is key. That makes it transition better, but you may need to confirm your library paths as well. I've got it working now, but it took longer than usual dot dot upgrades.