If I select "Add Account" and pick network "Facebook" the resulting screen shows me E-Mail and Passwort instead of Username and Passwort in the german locale. It is correct in the english version. Seen on jitsi win x64 on Windows 7 version 2.8.5426 (latest stable).
The dialog btw mentions I need to create a facebook username, it does not mention that I also should create a "app password" in case my fb account is "code protected". The resulting error message from facebook has no useful error code in the response xmpp message.
Facebook doesn't support XMPP anymore, so this is obsolete.