Currently, Unison 2.32.52 if compiled with 'gtk' flag is broken if used over SSH: The pop-up dialog for entering a password for an SSH private key does not come up (approximately 99 times out of 100). This used to work until an upgrade to other packages (not certain which would affect it). Recompiling Unison does not help.
Created attachment 262377 [details] emerge --info
This seems to be resolved now with the same version of Unison. Not certain an upgrade to what package solved the issue.