**Jerome’s Vulgate was not rendered from the LXX, but from the Hebrew as far as it went.
However, St. Jerome DID have access to Hebrew mss OLDER than the Masoretic text.
This is assuming that the Clementine Vulgate is the same as it left the pen of St. Jerome.**
Correct.

But Peter still gets one thing right in this: the Psalter included in most versions of the Vulgate were at least rendered from the LXX (the so-called “
Gallican Psalter”) - in fact St. Jerome made three versions of the Psalms: the
Versio Romana, the Gallican, and the
Versio juxta Hebraicum. The
Juxta Hebraicum, made from pre-Masoretic Hebrew manuscripts around the late 4th-early 5th century is included in a few early MSS, but it is not clear whether it was ever used in the liturgy as the Versio Romana and the Versio Gallicana had been.
Here’s one example of differences between the three (Psalm 94/95):
Versio Romana: Venite, exsultemus Domino; iubilemus
Deo salutari nostro. Praeoccupemus
faciem eius in
confessione, et in
psalmis iubilemus ei. Quoniam Deus magnus Dominus, et rex magnus super omnes deos.
Quoniam non repellet Dominus plebem suam,
quia in manu
ejus sunt omnes fines terrae, et
altitudines montium
ipse conspicit;
quoniam ipsius est mare, et ipse fecit illud, et
aridam fundaverunt manus eius.
Come, let us exult in the Lord; let us shout joyfully to God, our Savior; let us anticipate His presence in acknowledgement, and let us shout joyfully to Him with psalm: for the Lord is a great God, and a great King over all gods. Because the Lord will not drive off His people, for in His hand are all the ends of the earth, and He sees the heights of the mountains; for His is the sea, and He made it, and His hands established the arid land.
Versio Gallicana: Venite, exsultemus Domino; jubilemus Deo salutari nostro; praeoccupemus faciem ejus in confessione, et in psalmis jubilemus ei: quoniam Deus magnus Dominus, et rex magnus super omnes deos. Quia in manu ejus sunt omnes fines terrae, et altitudines montium ipsius sunt; quoniam ipsius est mare, et ipse fecit illud, et siccam manus ejus formaverunt.
Come, let us exult in the Lord; let us shout joyfully to God, our Savior; let us anticipate His presence in acknowledgement, and let us shout joyfully to Him with psalms: for the Lord is a great God, and a great King over all gods. For in His hand are all the ends of the earth, and the heights of the mountains are His; for His is the sea, and He made it, and His hands formed the dry land.
Versio juxta Hebraicum: Venite, laudemus Dominum; iubilemus petrae Iesu nostro. Praeoccupemus vultum eius in actione gratiarum: in canticis iubilemus ei. Quoniam fortis et magnus Dominus, et rex magnus super omnes deos. In cuius manu fundamenta terrae, et excelsa montium ipsius sunt. Cuius est mare; ipse enim fecit illud, et siccam manus eius plasmaverunt.
Come, let us praise the Lord; let us shout joyfully to the Rock of our Jesus. Let us anticipate His face in deeds of thanks: let us shout joyfully to Him with songs: for the Lord is strong and great, and a great King over all gods. In His hands are the foundations of the earth, and the heights of the mountains are His; His is the sea, for He made it, and His hands fashioned the dry land.
Interesting how St. Jerome rendered the Hebrew
tzur yish’ainu (“Rock of our salvation”) as
petrae Iesu nostro, taking the word
yesha, ‘salvation’, as a proper name - in this case, connecting it with ‘
Iesus’.