It appears that most posters here don't know that Tertullian's "Against Marcion" is really from an unknown source. It is virtually impossible to determine which version of "Against Marcion" is in circulation since the very preface of the existing copy claims there are at least three versions in circulation.
Against Marcion 1
Whatever in times past we have wrought in opposition to Marcion, is from the present moment no longer to be accounted of.
It is a new work which we are undertaking in lieu of the old one. My original tract, as too hurriedly composed, I had subsequently superseded by a fuller treatise.
This latter I lost, before it was completely published, by the fraud of a person who was then a brother, but became afterwards an apostate. He, as it happened, had transcribed a portion of it, full of mistakes, and then published it.
The necessity thus arose for an amended work; and the occasion of the new edition induced me to make a considerable addition to the treatise.
This present text, therefore, of my work — which is the third as superseding the second, but henceforward to be considered the first instead of the third — renders a preface necessary to this issue of the tract itself that no reader may be perplexed, if he should by chance fall in with the various forms of it which are scattered about.
Is this the first, second or third version?
Please, tell me what did Tertullian write about Marcion before this version?
The fact is that Tertullian's "Against Marcion" was unknown by Christian writers up to at least the start of the 5th century.
Look at Eusebius' Church History.
Church History supposedly written around c 325 CE mentions 10 Christians who wrote against Marcion--not once did it claim Tertullian wrote against Marcion.
Justin, Irenaeus, Hippolytus, Dionysius, Theophilus, Philip, Modestus, Bardesanes, Rhodo and Militades all wrote against Marcion in Eusebius' "Church History". [See Church History bk 4, 5 and 6]
Look at "De Viris Illustribus" supposedly written about c 395 CE by Jerome. This writings also mentions those who wrote Against Marcion and again Tertullian is missing.
In De Viris Illustribus -- Justin, Irenaeus, Hippolytus, Theophilus, Philip, Modestus, Bardesanes and Rhodo are claimed to have written against Marcion but not Tertullian.
Jerome claimed that Tertullian became a heretic [a Montanist] who wrote Against the Church.
Jerome's DeViris Illustribus"
Of his fine oratorical genius, Tertullian, in the seven books which he wrote against the church on behalf of Montanus, satirically says that he was considered a prophet by many of us.
Jerome's DVI 40
Tertullian added to the six volumes which he wrote On ecstasy against the church a seventh, directed especially against Apollonius
Jerome's DVI 53 He[Tertullian] composed, moreover, directly against the church, volumes: On modesty, On persecution, On fasts, On monogamy, six books On ecstasy, and a seventh which he wrote Against Apollonius.
There is no corroborative evidence that Tertullian wrote against Marcion up to at least the 5th century and even worse multiple Christian writings do not support the claims about Marcion found in "Against Marcion" attributed to Tertullian.
Tertullian was a Montanist who wrote directly against the Church.