Sequencing nucleic acids (RNA, DNA) is more straightforward, though protein sequencing tech is fairly functional too, if more expensive and complicated, machinery wise.
“Multiple rereads of single proteins at single–amino acid resolution using nanopores”: https://www.science.org/doi/10.1126/science.abl4381
(Unfortunately paywalled, but the senior author explained the paper in a Twitter thread: https://twitter.com/cees_dekker/status/1456323490647212033)