The standard email to contact Freetrade is hello@freetrade.io but there are also some more specific email addresses, which may or may not apply:
If you are fine with using the original email address you used to login for your first FT account, I’d email them from that and keep it going forwards. If you want to use a different one for login going forwards it may get more complicated, honestly.
Obviously if you’re logged in to the app you have a better chance of accessing support than you would outside of it, but I agree it’s not super helpful (although I did get the regular email from the help articles on the FT website).