@woozle probably the federation_hint_html i18n variable in en_GB.yml (and whichever other locale our instance supports.
@woozle and see app/views/auth/confirmations/new.html.haml and auth.resend_confirmation or perhaps auth.confirm_email in the locales for the other view you mentioned.
@woozle see https://github.com/glitch-soc/mastodon/blob/main/app/views/about/_registration.html.haml for the actual template with all the used #i18n variable names for that view.