Using the devuan_ascii_2.0.0_amd64_dvd-1.iso image from a USB stick I
consistently get the error:

    [!] Detect and mount CD-ROM
    Error reading Release file
    The CD-ROM does not seem to contain a valid 'Release' file,
    or that file could not be read correctly.

    You may try to repeat CD-ROM detection but, even if it does
    succeed the second time, you may experience problems in the
    installation.

If it's any clue, the same error also occurs on the
devuan_ascii_2.0.0_amd64_cd-1.iso image as well as the Debian-based
2018-06-27-rpd-x86-stretch.iso image for Raspbian. So the problem may
be upstream.

/Lars