Hi, thanks for sharing this mess.
A note: if you are not from a state of the European Union or at least you don't live in one,, the CLI might ignore your request as the GDPR only apply to EU citizen (theoretically everywhere in the world) or to non-EU citizen while they are in a EU state.
In such case though I think you could anyway get your deadname changed by requesting it under French copyright that is slightly different from common law copyright.
Indeed, in states under the civil law tradition, authors of a work have some unalienable (also unsellable) moral rights, among which the right to correct attribution.
If SWH is misattributing your work, you have the right to get it fixed, even if you are not a European citizen.
(note I'm a European citizen, but not a lawyer)
Having said that, are you sure your deadname is still there?
As far as I can see here https://archive.softwareheritage.org/browse/snapshot/e41242466c8847f83000ff1242edf1ae78202688/log/?origin_url=https://github.com/rspeer/python-ftfy you are referred through your names (both married and maiden ones).
Maybe they finally fixed the issue?
@arborelia
As for GitHub's forks: have you considered a DCMA takedown to the forks that still attribute your code to your deadname?
After all, they are all violating your copyright, distributing copies of your work with a wrong attribution to someone that does not exists (anymore)!