Here the 1906 LDS edition changed the conjunction but to and, perhaps intentionally since the verb hail seems positive in meaning, in agreement with the meaning ‘to salute, greet; to welcome’ (the first definition for the second verb hail listed in the Oxford English Dictionary). But actually the meaning here in Alma 55:8 is more related to the third definition under that verb in the OED: ‘to call or shout to from a distance, in order to attract attention’. Basically the guards are challenging the approach of Laman since he could be an enemy. There is an underlying negative implication in the use of the verb hail here, thus the use of the but to reverse the polarity. The 1906 edition was never used as a copytext, so this secondary and is restricted to that edition. The critical text will maintain the original but here in Alma 55:8 since it is the reading of the earliest textual sources (including 𝓞) and is wholly appropriate.
Summary: Maintain here in Alma 55:8 the conjunction but (the original reading) since it reverses the polarity of the preceding verb hail; in this verse hail means ‘to challenge’ and has a negative implication.