‘Along’ is a preposition or an adverb. In the iWeb corpus the tagging by part of speech:
1 ALONG WITH (II21) 1742449 (two-part complex prepositional phrase)
Within the next forty-eight hours,
you, along with the rest of the Wizarding World,
will choose our next great leader.
2 ALONG (II) 812587
4 ALONG (RP) 476307
6 ALONG (RR) 11996