Does your chapel use the Advent preface? My SSPX one doesn't, but it does appear on the DivinumOfficium.org missal—e.g., for today (4^th Sunday of Advent) or during the week in Advent (e.g., last Saturday of Advent):

de Adventu Vere dignum et iustum est, æquum et salutáre, nos tibi semper et ubíque grátias ágere: Dómine, sancte Pater, omnípotens ætérne Deus: per Christum Dóminum nostrum. Quem pérdito hóminum géneri Salvatórem miséricors et fidélis promisísti: cuius véritas instrúeret ínscios, sánctitas iustificáret ímpios, virtus adiuváret infírmos. Dum ergo prope est ut véniat quem missúrus es, et dies affúlget liberatiónis nostræ, in hac promissiónum tuárum fide, piis gáudiis exsultámus. Et ídeo cuм Angelis et Archángelis, cuм Thronis et Dominatiónibus, cuмque omni milítia cœléstis exércitus, hymnum glóriæ tuæ cánimus, sine fine dicéntes:

Advent It is truly fitting and proper, right and profitable to salvation, that we should at all times and in all places give thanks to You, Lord, holy Father, Almighty and everlasting God, through Christ our Lord. For You have promised Him, O faithful and merciful One, as a Saviour for the lost human race; so that His truth might instruct the ignorant, His holiness might sanctify sinners, and His power might strengthen the weak. Since, therefore, the time of His coming is near, and the day of our liberation is dawning, we trust in Your promises and exult with joyous love. And, therefore, with Angels and Archangels, with Thrones and Dominations, and with the whole host of the heavenly army, we sing a hymn to Your glory, saying without ceasing:

I can't find it in my 1962 or 1920 missals, though they do have the Præfatio de Nativitate. Is the Advent Preface a post-1962 novelty?

The Advent Preface is amongst the so-called Gallican Prefaces.

Interesting. Thanks.
FIUV Positio N. 8 Prefaces says the Advent Preface is part of the "Paris Missal (‘de Vintimille’) of 1738" and "Neo-Gallican Missal of 1738".