Comment 6 for bug 2012028

Interesting, jammy in a container also lacks the versions but works fine:

    <tpm supported='yes'>
      <enum name='model'>
        <value>tpm-tis</value>
        <value>tpm-crb</value>
      </enum>
      <enum name='backendModel'>
        <value>passthrough</value>
        <value>emulator</value>
      </enum>
    </tpm>

But the define of that minimal guest XML works.
That also explains why I thought I've seen both outputs on jammy, one in the container one on my laptop.
So the disappearing of the versions from domcapabilities might have been a red herring.

I've now settled on a test env that uses Kinetic and Lunar (closest in versions) both in containers (same environment) and just using the definition of that minimal xml (simpler case for debugging).