I want to create my own deb repository to store some packages. I've tried reprepro and it works fine, except one but fundamental feature. Reprepro can't store several versions of the same package in the repository.

But the ability to store several versions of the same package is essential to me, so I'm asking what soft can do such a thing.

Here is a piece of reprepro FAQ that shows that it can't do it:

3.1) Can I have two versions of a package in the same distribution?
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Sorry, this is not possible right now, as reprepro heavily optimizes
at only having one version of a package in a suite-type-component-architecture
quadruple.
You can have different versions in different architectures and/or components
within the same suite. (Even different versions of a architecture all package
in different architectures of the same suite). But within the same
architecture and the same component of a distribution it is not possible.