Here the earliest text has the singular possession in verse 33, followed by the plural possessions in verse 34. The 1874 RLDS edition eliminated the difference in number by changing the plural in verse 34 to the singular; for that instance of possession(s) the 1908 RLDS edition restored the plural to the RLDS text.
For the first instance of possession(s), the original manuscript is extant. Oliver Cowdery initially wrote possesion (that is, with one s before the -ion ending). He corrected the spelling by inserting an s supralinearly above the i. This correction should probably not be interpreted as adding a plural s to the end of the word. In other instances, Oliver normally corrected a missing final s by inserting it in the space at the end of the word. If he did insert the letter supralinearly, it was always near the end of the word. Thus the supralinear s above the i in 𝓞 probably indicates an attempt on Oliver’s part to correct the spelling from possesion to possession.
One could argue here that Oliver Cowdery’s correction in 𝓞 of possesion to possession in Alma 22:33 could have distracted him from noticing that he had accidentally omitted a plural s. In support of the plural, we not only have the plural in the next verse (“the Lamanites could have no more possessions / only in the land of Nephi”) but also the plural in the one other occurrence of “no more possession(s)” in the Book of Mormon text, in Helaman 4:18: “Moronihah could obtain no more possessions over the Lamanites”. Thus in two out of three instances, the earliest reading has the plural “no more possessions”.
There is some evidence that Oliver Cowdery occasionally mixed up the number for possession(s), although in each case the error was an initial one in 𝓟 and was corrected virtually immediately by him:
In the first case, the initial error was the singular possession, but in the two other cases, the initial error was the plural possessions.
As discussed under 2 Nephi 29:14, either possession or possessions is possible for the phrase “the land(s) of one’s possession(s)”. The same decision should probably be made with respect to the phrase “no more possession(s)”, especially since there are only three instances of the phrase in the text. In other words, in each case we follow the earliest textual sources, which means that the critical text will accept the occurrence of both “no more possession” and “no more possessions” in Alma 22:33–34.
Summary: In accord with the earliest textual sources, accept the singular “no more possession” in Alma 22:33 and the plural “no more possessions” in Alma 22:34 and in Helaman 4:18.