::
there isn’t actually anything binding you to use „username@server.com“ only for server.com when logged in as username.
just generate the key that you want, put it in authorized_keys where you want it, and run the appropriate command, e.g., `trezor-agent username@server.com — ssh root@somewhere-else.com`
personally, however, I generate separate public keys per server. It’s nice to have Trezor show you where you’re logging in. It’s a little more tedious than the opposite, true, but not by much IMHO and you have some small niceties such as `trezor-agent -s name@server` which will open a ssh session directly