I've found some inconclusive but interesting information.
LinkedIn logged in user on archives
As of 2020, all archives of LinkedIn archives appear to be under the same account, e.g.:
Searching by the image on Google, leads to the following LinkedIn Account "Masha Rabinovich" https://www.linkedin.com/in/masha-rabinovich-52aa3a197/ which is marked as being a Bachelor of Engineering Bachelor at the Humboldt University of Berlin. These accounts keep getting deleted apparently by LinkedIn, here's one live as of 2023: https://www.linkedin.com/in/masha-rabinovich-7b56a5125/
Further Google searches for that name lead to several online threads that create a convincing profile of that name being the creator of archive.is, perhaps most notably from 2012-08 https://community.f-secure.com/en/discussion/14768/what-is-the-evidence-of-harmful-behaviour#M3733 a user named "masharabinovich" mentions:
Your website http://browsingprotection.f-secure.com/swp/result?x=5Jg2kWKC8d86b4F-H5cdoS8dyu04vtzGtEXhQL6COLIX0k4wrv-N*w shows that someone in your company "found evidence of harmful behaviour" on my website http://archive.is/
It is not certain that Masha is a real identity at all, but taken together, it feels very possible that whoever is behind that account is the creator of the website.
Wikipedia suggests that the name Masha Rabinovich is likely of Russian Ashkenazi Jewish origin:
so if the LinkedIn information is real, maybe they just went to study in Germany, or their ancestors migrated there.
GitHub logged in user on archive
Their logged in GitHub from archives gives even more information. They later deleted most of their GitHub activity, but archives remain.
https://discourse.nixos.org/t/how-was-this-treewide-pr-performed/11174/15 confirms the brutal account deletion applied also mentioned at: https://twitter.com/grhmc/status/1334138105738256389 but those threads didn't know about archive.is.
What I don't understand however is how it is possible that I can still make archives today as of 2021-02-08 and they are logged in as volth, but the volth homepage is still a 404 at the very same time!!! The only explanation I can think of is that GitHub has a shadowban mode, where the user can still login, but not make any contributions, and all past contributions are hidden, related: https://stackoverflow.com/questions/50720844/can-github-delete-your-account/66105692#66105692