Answered by Ustadh Tabraze Azam
Some mosques have two speeches on Friday. The first one is given by the Imam after the first call to prayer in Urdu. The actual Friday sermon is in Arabic and takes place after the second call to prayer.
Would it still be disliked to offer a voluntary prayer when the Imam is giving the first speech?
You should treat such a lecture as you would treat the official sermon (khutba).
However, if you need to make a missed prayer or prayers, and you have less than six in your dues, then this would take precedence, as it does in the official sermon, because the Friday prayer would not be valid without it.
[Tahtawi, Hashiyat al-Tahtawi `ala Maraqi al-Falah (2.134)]
And Allah Most High alone knows best.
Checked & Approved by Shaykh Faraz Rabbani