The AdminVM is based on Fedora and has systemd, but it has no network and you you shouldn't run anything there. Unless you think that systemd is actively malicious and specifically targets Qubes, any vulnerabilities in it are not exploitable.
Thanks for the info. I went through what I had thought was enough Show posts to find it, but apparently not enough :-( I haven't been on Hacker News in a few years and forgot how it works - I should have checked my submissions section.
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