To connect to instance, your SSH client must support newer standards.
Those who are unaware of the following change may find that they cannot connect to this type of instance with SSH. (It loses a star because this requirement was not apparent and required no little effort to uncover.)
With the 22.04 Jammy Jellyfish release, an older, vulnerable standard for SSH communication has been deprecated. That is an improvement in security, but it has consequences that can mysteriously cause grief to those who are not forewarned.
PuTTY 0.74 or earlier won't connect via SSH. (Upgrade to PuTTY 0.76 or later.) The current latest WinSCP (5.19.6) or earlier also will not connect via SSH, but version 5.20 (currently in beta) will.
On the plus side, besides being a very popular distribution, Ubuntu instances (along with Amazon Linux and Windows) are eligible for AWS Per Second Billing.
https://aws.amazon.com/ec2/pricing/
Of course, the Ubuntu LTS images get the additional advantage of Long Term Support.
Thanks for this comment - it lead me to fixing the problem I was having with accessing the machine. In my case, I was using packer to build AMIs. Skimming the packer release notes lead me to version 1.8.1, which includes the new SHA-2 algos in the golang crypto implementation. (https://github.com/hashicorp/packer/releases/tag/v1.8.1) Once I updated to that version of packer, it was able to access the AMI and begin provisioning.