Comment 4 for bug 1943833

Brian is correct, I just tried to reproduce it on a different 21.04 system and it passes without a hitch as well.

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fwupdmgr refresh
WARNING: UEFI firmware can not be updated in legacy BIOS mode
  See https://github.com/fwupd/fwupd/wiki/PluginFlag:legacy-bios for more information.
Updating lvfs
Downloading… [***************************************]
Downloading… [***************************************]
Successfully downloaded new metadata: 0 local devices supported
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apt-cache policy fwupd libjcat1
fwupd:
  Installed: 1.5.11-0ubuntu1~21.04.1
  Candidate: 1.5.11-0ubuntu1~21.04.1
  Version table:
 *** 1.5.11-0ubuntu1~21.04.1 500
        500 http://fr.archive.ubuntu.com/ubuntu hirsute-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.5.8-0ubuntu1 500
        500 http://fr.archive.ubuntu.com/ubuntu hirsute/main amd64 Packages
libjcat1:
  Installed: 0.1.3-2
  Candidate: 0.1.3-2
  Version table:
 *** 0.1.3-2 500
        500 http://fr.archive.ubuntu.com/ubuntu hirsute/main amd64 Packages
        100 /var/lib/dpkg/status
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As a result I tried the initial system again and it also passed.

People in the upstream bug report to have seen similar behaviour as well, where it magically works in the weekend but not during the week.