Hello!
Yes, we just don`t packaging it, because it is not very widespread and there was no requests from users for us to do so.
But I assume you are requesting it now, right?

No. I do research and find solutions for my tasks. I consider different decisions. There are requirements for the operating system (should work on Astra Linux 1.6.), so clarified about the possibility of working under a specific OS, which did not see in the list of supported

It is supported just like any Linux distribution, that PostgreSQL supports.
Binaries can be compiled.
We just don`t packaging those binaries for Astra.
But we can start doing that if there is a demand for it.

It can be actual to government customers
We have some government projects on AstaLinux and we will be happy to use probackup on them
As example

$ lsb_release -a
No LSB modules are available.
Distributor ID: AstraLinuxCE
Description:    Astra Linux CE 2.12.42 (Orel)
Release:        2.12.42
Codename:       orel

Hello!
Ok, I suppose we can do that.

$ lsb_release -a
No LSB modules are available.
Distributor ID: AstraLinuxCE
Description: Astra Linux CE 2.12.42 (Orel)
Release: 2.12.42
Codename: orel

As example, for this Astra version may be used packages for stretch release
I install it now and it's looks like workable

Добавил инструкции по установке
https://github.com/postgrespro/pg_probackup#linux-installation