This bug is similar to bug 4436. When using public key authentication, it would be nice if we could use keys held in a running ssh-agent. As far as I can tell, this does not work, since we are clearing SSH_AUTH_SOCK regardless of authentication type.
https://community.thinlinc.com/t/using-ssh-key-agents-with-the-thinlinc-client/444
Another benefit of this would be the ability to use GPG sub-keys to authenticate with ThinLinc via gpg-agent. gpg-agent supports ssh-agent emulation, so in theory we should get this feature "on the house". Extracting a GPG sub-key in SSH format is non-trivial these days, so those who use gpg-agent for SSH authentication will have a hard time using the same key with ThinLinc.
*** Bug 8233 has been marked as a duplicate of this bug. ***
macOS apparently has the weird setup where the key is still stored on disk, but the passphrase for it is stored in the keychain: https://apple.stackexchange.com/questions/48502/how-can-i-permanently-add-my-ssh-private-key-to-keychain-so-it-is-automatically I am not sure if that's within scope here or not.