There are some recent startups (Glyphic Bio out of MIT, and Jonathan Rothberg's Quantum-Si) that are tackling next-gen protein sequencing. I'm eager to see what they can do once they're widely available.
“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)