I tried git-bug a few months ago, and https://github.com/git-bug/git-bug/issues/1023 is a showstopper.
There is a workaround, but it isn't pretty. You can push/pull bugs and identities with normal, ssh-agent-less git commands: https://gist.github.com/parasyte/80ef925d4b01216f6bcb051356f...
Isn't "show stopper" a bit dramatic? What is the big problem with an SSH agent? If security is a problem you should probably store your SSH keys on a HSM like a Nitrokey or Yubikey. In which case you need an agent.
I'll fix that soon. I really wanted to avoid calling the git binary for security reason, but I have to admit that go-git is not robust enough in some cases. I'll have at least the option to use the git binary for push/pull, possibly as a default depending on how it goes.