Conversion of Debian sid to versions is done based on Debian codenames.
The version number is the version number of the final release - 0.01.
It is unknown if Debian < 4.0 has any sort of version information
available (apart from maybe checking base-files package version).
But I don't think any of these systems are still alive,
so I think going with 3.99 is fine for those.
All distros with ID_LIKE suse should be treated as "suse".
My openSUSE Leap 15.1 installation has:
This patch doesn't require a strict "suse" value but only the word suse to be in
ubuntu 6.10 and debian etch are 10+ years old and EOL. rather than
preserving compatibility I'll just remove it. while /etc/environment
works too, correct place is /etc/default/locale (as it was before
breaking change). also /etc/debian_version (os_version explorer) may
contain minor version with dot (10.5) or string (bullseye/sid).