I am cross-compiling gftp in OpenEmbedded. With 2.6.0b (September 2020) and the latest 2.7.0b source (2021-04-07), neither work when there is a new ssh2 connection.
The old version that I previously compiled in OE, 2.0.19 with patches from debian and a couple from elsewhere, works fine.

The text window shows this:

The authenticity of host 'bkhome.org (216.239.139.38)' can't be established.
RSA key fingerprint is SHA256:m92efZZcaMaF5T0ATctW4YOwS9olCNxp7oAvlYnxsyu.
Are you sure you want to continue connecting (yes/no/[fingerprint])?

That is also supposed to popup in a gtk window, with yes/no buttons, but that doesn't happen.
I ran gftp from a terminal window, there is no error message.