What Linux Kernel Versions are Acceptable for AMI Import to Amazon Web Services?

I had the same problem with my kernel version not being supported. In August of 2019, the kernel-5.0.0 on my Ubuntu-18.04.2 was not accepted. To compare what Amazon's AMIs were using, I launched their Ubuntu-18.04.2 and found that it was using kernel-4.4.0. So I ended up using an Lubuntu-16.04.3.VMDK that I had locally with kernel-4.10.0-28-generic, converted it to .OVA (OVF version 2.0) using VirtualBox, uploaded it to S3, and was able to successfully get it to import to .AMI using the "aws ec2 import-image" command. So based on my tests, it seems that as of now, AWS is accepting kernel-4, but not kernel-5. Hope this helps!