Here scribe 2 of 𝓟 wrote “but this much I know”, which is what we might expect in modern English. Oliver Cowdery corrected the text here by inserting the auxiliary verb do: “but this much I do know”. Either reading is possible, which suggests that Oliver’s correction was the reading in 𝓞. It is doubtful that he would have consciously edited the text here since “but this much I know” reads perfectly well. Elsewhere the original text has 99 occurrences of I know but also 7 of I do know:
Thus the critical text will follow the corrected reading in 𝓟 for Alma 7:8: “but this much I do know”.
Summary: Maintain in Alma 7:8 Oliver Cowdery’s corrected reading with the auxiliary verb do (“but this much I do know”).