Version 0.10.3 is available upstream. If sensible, I would like this to be available in the main portage tree. A simple copy of pam_ssh_agent_auth-0.10.2 to pam_ssh_agent_auth-0.10.3 compiles and functions for me. My reason is that this adds ed25519 keys support. Thanks for your time!
0.10.3 is in the tree since Fri Nov 2 12:46:01 2018 -0400