Changing default crontab editor

Just simply run select-editor, this will let you choose any editor you want.

Try your ssh session followed by

export EDITOR=vim

or possibly

export EDITOR=/usr/bin/vim.basic

The format of setting of the EDITOR variable depends on which shell you are using.

In Ubuntu you can set the EDITOR environment variable on logon by adding the above to the ~/.profile

Your SSH session will read a similar file (if it exists) on the remote host called ~/.ssh/environment. This has to be specifically defined by the ssh daemon config. See man sshd_config and look for PermitUserEnvironment for more details.