Clifford P. Jones argues that the Lamanite "mark" was an ancient tattoo (sacrilegious mark) and has nothing to do with natural skin color.
Clifford P. Jones, "Understanding the Lamanite Mark," Interpreter: A Journal of Latter-day Saint Faith and Scholarship 56 (2023): 171-258
Abstract: The Book of Mormon describes a dark mark on the skin that distinguished people who rebelled against God and his laws from those who obeyed God. The Old Testament refers to a mark that fits this description and has nothing to do with natural skin color. The law of Moses prohibited the Lord’s covenant people from cutting sacrilegious marks (ancient tattoos) into their skin. The Bible simply calls these prohibited tattoos “marks” (Leviticus 19:28). This biblical meaning of the word mark, together with biblical meanings of other related words, helps us understand all Book of Mormon passages associated with the Lamanite mark.