Just start with Linux mint and cinnamon or kde desktop environment. You should be good to go with that. Kernels are not something that you usually need to worry about, the default should work fine. If you need to, it’s easy to switch to another kernel by just installing it through the package manager.
Kubuntu uses snaps as default and I’ve had some trouble with that. My dad is using Kubuntu and there are problems with how programs communicate. Mint is probably a better choice.