Following are a number of back-translations as well as a sample translation for translators of Jeremiah 48:30:

• Kupsabiny: “I God know their rebellion
  but that boasting of theirs is empty/futile.” (Source: Kupsabiny Back Translation)
• Hiligaynon: “I, the LORD, knows how boastful you are, but it is worthless.” (Source: Hiligaynon Back Translation)
• English: “But Yahweh says, ‘I know about that,
  but it is useless for them to boast
  because it will accomplish nothing.” (Source: Translation for Translators)