Yes, I’m on Debian 10 (Buster), which has glibc 2.28

A fully upgraded Ubuntu 20.04 would have glibc 2.31, 18.04 would have 2.27.

I suspect the problem might be this issue, which suggests that it would trigger upon upgrading to glibc >= 2.28.

But, if it’s working for you on Ubuntu 20.04, that may not be it.

Is gl_image downloading a pre-built mksquashfs4? I might try building that locally and substituting it in, which would eliminate glibc version compatibility issues.