Problem to access ssh
After several attempts configuring instances for arm and x64, it has not been possible to access the instance via ssh to port 22 with the user "ubuntu". We already verified the correct configuration of the security group.
I ran into the same problem as you did, but eventually found the source of the problem. See my own review with the title "To connect to instance, your SSH client must support newer standards." That review will explain how one needs to use client tools that support some newer standards.