To provide all the features in a package such as a fallback priority through the installed fonts on the system, We need to address an issue how to deal with a config file too.

We can't simply bind-mount /etc/fonts/conf.d from the host to a container/toolbox because they could have same files from packages installed on a container. To avoid conflict, we need to move it to other directory though, that breaks the order of files because fontconfig currently can't flatten config files through directories.
Let's see, given that we have the following files:

conf.d
 |- dirA
 |  |- 40-foo.conf
 |  |- 50-bar.conf
 |- dirB
 |  |- 10-baz.conf
 |  |- 20-qux.conf

And also given that dirA comes from the host and dirB comes from a container.

On the host, even if installing those all packages, the order of files to process would be simply 10->20->40->50. but On a container which has the above layout, if they have a config to read directories in order of dirA and dirB, it would be 40->50->10->20.

This makes ovious difference between them and particularly be a problem.

For Toolbx there is this ticket now: https://github.com/containers/toolbox/issues/1594

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/i18n/i18n/issues/191

Please continue any further discussion there.