When the site lists its fingerprint as something like
SSH2/RSA 2048 86:7b:1b:12:85:35:8a:b7:98:b6:d2:97:5e:96:58:1d
(Note, I am not trying to mirror keys here. If anyone reading this needs the keys for some site, such as the one I linked to above at one point, that person should go to the site itself, and complain loudly if keys can't be found.)
That format is the old, less secure MD5 format.
Go into the ssh configuration file for the user, probably something like
and add or uncomment this line:
But be sure to comment it back out when done, so you use the more secure protocol options instead.
(Should edit this when I'm awake again to add the site specifier line, which partially mitigates the problem of choosing the less secure protocol options. And otherwise say more sensible things.)
(Also need to complain loudly to said site about not publishing the SHA256 fingerprint keys yet.)